US20180090671A1 - Magnetoresistive element and magnetic memory device - Google Patents
Magnetoresistive element and magnetic memory device Download PDFInfo
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- US20180090671A1 US20180090671A1 US15/699,749 US201715699749A US2018090671A1 US 20180090671 A1 US20180090671 A1 US 20180090671A1 US 201715699749 A US201715699749 A US 201715699749A US 2018090671 A1 US2018090671 A1 US 2018090671A1
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- H01L27/228—
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- H01L43/02—
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- H01L43/10—
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B61/00—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10B61/20—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors
- H10B61/22—Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices comprising components having three or more electrodes, e.g. transistors of the field-effect transistor [FET] type
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/10—Magnetoresistive devices
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/80—Constructional details
- H10N50/85—Magnetic active materials
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N50/00—Galvanomagnetic devices
- H10N50/80—Constructional details
Definitions
- Embodiments described herein relate generally to magnetoresistive element and a magnetic memory device.
- the magnetoresistive element that uses a MTJ (Magnetic Tunnel Junction) element.
- the MTJ element uses, for example, the tunneling magnetoresistive (TMR) effect.
- TMR tunneling magnetoresistive
- the magnetoresistive element is, for example, a memory cell of a magnetic memory device such as magnetic random access memory (MRAM), etc. It is desirable for the magnetoresistance ratio of the magnetoresistive element to be high.
- FIG. 1A and FIG. 1B are schematic cross-sectional views illustrating a magnetoresistive element according to a first embodiment
- FIG. 2 is a graph illustrating a characteristic of the magnetoresistive element according to the embodiment
- FIG. 3A to FIG. 3E are photographs illustrating the analysis results of the magnetoresistive element
- FIG. 4A and FIG. 4B are graphs illustrating analysis results of the magnetoresistive element
- FIG. 5 is a graph illustrating characteristics of the magnetoresistive element
- FIG. 6 is a graph illustrating a characteristic of the magnetoresistive element
- FIG. 7 is a schematic cross-sectional view showing the other magnetoresistive element according to the first embodiment
- FIG. 8 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 9 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- FIG. 10 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 11 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 12 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 13 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 14 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 15 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 16 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment
- FIG. 17 is a schematic cross-sectional view illustrating a magnetic memory device according to a second embodiment
- FIG. 18A to FIG. 18E are schematic cross-sectional views illustrating the method for manufacturing the magnetic memory device according to the second embodiment
- FIG. 19 is a schematic view illustrating the magnetic memory device according to the second embodiment.
- FIG. 20 is a schematic view illustrating a magnetic memory device according to the second embodiment.
- FIG. 21 is a schematic view illustrating another magnetic memory device according to the second embodiment.
- a magnetoresistive element includes a first magnetic layer, a second magnetic layer, and a first nonmagnetic layer.
- the first nonmagnetic layer is provided between the first magnetic layer and the second magnetic layer.
- the first nonmagnetic layer includes an oxide including an inverse-spinel structure.
- a magnetoresistive element includes a first magnetic layer, a second magnetic layer, and a first nonmagnetic layer.
- the first nonmagnetic layer is provided between the first magnetic layer and the second magnetic layer.
- the first nonmagnetic layer includes an oxide including Ga.
- the oxide has a plurality of photon energy peaks corresponding to a binding state of the Ga included in the oxide in X-ray absorption near edge structure analysis.
- a magnetoresistive element includes a first magnetic layer, a second magnetic layer, and a first nonmagnetic layer.
- the first nonmagnetic layer is provided between the first magnetic layer and the second magnetic layer.
- the first nonmagnetic layer includes an oxide.
- the oxide includes Mg, Ga, and oxygen.
- the oxide has a first peak intensity of a first photon energy, a second peak intensity of a second photon energy, and an intermediate intensity of a third photon energy in a photon energy range not less than 10370 electron volts and not more than 10385 electron volts in X-ray absorption near edge structure analysis.
- the second photon energy is larger than the first photon energy.
- the third photon energy is between the first photon energy and the second photon energy.
- the intermediate intensity is lower than the first peak intensity and lower than the second peak intensity.
- FIG. 1A and FIG. 1B are schematic cross-sectional views illustrating a magnetoresistive element according to a first embodiment.
- the magnetoresistive element 110 includes a first magnetic layer 11 , a second magnetic layer 12 , and a first nonmagnetic layer 11 N.
- the first nonmagnetic layer 11 N is provided between the first magnetic layer 11 and the second magnetic layer 12 .
- the first magnetic layer 11 is, for example, a ferromagnetic layer.
- the second magnetic layer 12 is, for example, a ferromagnetic layer.
- the first nonmagnetic layer 11 N is, for example, a tunneling barrier layer.
- the first nonmagnetic layer 11 N includes an oxide.
- a base layer 10 S and a second nonmagnetic layer 12 N are provided in addition to the first magnetic layer 11 , the second magnetic layer 12 , and the first nonmagnetic layer 11 N.
- the first magnetic layer 11 is provided between the base layer 10 S and the second magnetic layer 12 .
- the second nonmagnetic layer 12 N is provided between the first magnetic layer 11 and the first nonmagnetic layer 11 N.
- the second nonmagnetic layer 12 N is, for example, a nonmagnetic metal layer. There are cases where the boundary between the second nonmagnetic layer 12 N and the first nonmagnetic layer 11 N is indistinct. In the case where the second nonmagnetic layer 12 N is thin (e.g., 0.6 nm or less), the second nonmagnetic layer 12 N and the first nonmagnetic layer 11 N may be observed as one layer.
- various layers other than the first magnetic layer 11 , the second magnetic layer 12 , and the first nonmagnetic layer 11 N may be provided.
- the electrical resistance between the first magnetic layer 11 and the second magnetic layer 12 changes when energy (e.g., at least one of a magnetic field, an electric field, a current, a voltage, or stress) is applied to the magnetoresistive elements 110 and 110 A.
- energy e.g., at least one of a magnetic field, an electric field, a current, a voltage, or stress
- the change of the electrical resistance is based on the magnetoresistance effect.
- the direction of at least one of the magnetization of the first magnetic layer 11 or the magnetization of the second magnetic layer 12 changes according to the applied energy.
- the angle between these magnetizations changes according to the applied energy.
- the first magnetic layer 11 functions as, for example, a free layer.
- the first magnetic layer 11 functions as, for example, a memory layer.
- the second magnetic layer 12 functions as, for example, a reference layer.
- a first direction that connects the first magnetic layer 11 and the second magnetic layer 12 is taken as a Z-axis direction.
- One direction perpendicular to the Z-axis direction is taken as an X-axis direction.
- a direction perpendicular to the Z-axis direction and the X-axis direction is taken as a Y-axis direction.
- the first direction corresponds to the stacking direction of the first magnetic layer 11 , the first nonmagnetic layer 11 N, and the second magnetic layer 12 .
- the first nonmagnetic layer 11 N has a face 11 Na crossing the first direction (the Z-axis direction).
- the face 11 Na is, for example, a face opposing the first magnetic layer 11 .
- the face 11 Na is aligned with the ⁇ 100 ⁇ plane.
- the face 11 Na may not be perfectly parallel to the ⁇ 100 ⁇ plane and may be, for example, tilted.
- the angle between the face 11 Na and the ⁇ 100 ⁇ plane may be, for example, 10 degrees or less.
- the ⁇ 100 ⁇ plane may be, for example, the plane of the crystal orientation of the first magnetic layer 11 .
- the thickness of the first nonmagnetic layer 11 N (a first nonmagnetic layer thickness t 1 referring to FIG. 1A ) is, for example, not less than 0.2 nm (nanometers) and not more than 4 nm. For example, an appropriate tunneling barrier effect is obtained using such a thickness. As described below, a high magnetoresistance ratio is obtained using such a thickness.
- the first nonmagnetic layer thickness t 1 is the length of the first nonmagnetic layer 11 N along the first direction (the Z-axis direction).
- the first nonmagnetic layer thickness t 1 may be, for example, not less than 1.1 nm and not more than 3.3 nm.
- the first nonmagnetic layer thickness t 1 may be, for example, not less than 1.1 nm and not more than 3.0 nm.
- the first nonmagnetic layer thickness t 1 may be, for example, not less than 1.1 nm and not more than 2.8 nm.
- the first nonmagnetic layer 11 N includes an oxide.
- the oxide includes, for example, Mg and Ga.
- the oxide may include MgGa 2 O 4 .
- Other examples of the oxide included in the first nonmagnetic layer 11 N are described below.
- the oxide that is included in the first nonmagnetic layer 11 N includes an inverse-spinel structure. It was found that a high magnetoresistance ratio MR is obtained thereby. For example, a high magnetoresistance ratio MR is obtained while maintaining a low resistance area product RA.
- the magnetoresistance ratio MR is, for example, the tunneling magnetoresistance ratio (the TMR ratio).
- a sample (a first sample) of the experiment described below has the configuration of the magnetoresistive element 110 A.
- the base layer 10 S is a Cr layer.
- the first magnetic layer 11 is an Fe layer.
- the second nonmagnetic layer 12 N is a Mg layer.
- the thickness of the Mg layer is 0.6 nm.
- the first nonmagnetic layer 11 N is a MgGa 2 O 4 layer.
- the thickness of the MgGa 2 O 4 layer (the first nonmagnetic layer thickness t 1 ) is 3.0 nm.
- the second magnetic layer 12 is an Fe layer.
- the notation “first material name/second material name” may be used. This notation means that a layer of the first material name is provided on a layer of the second material name.
- the notation “first material name (first length)” may be used. This notation means that the thickness of a layer of the first material name is the first length.
- the notation “Fe/MgGa 2 O 4 ( 3 . 0 nm)” corresponds to the state in which an Fe layer is provided on a layer of MgGa 2 O 4 having a thickness of 3.0 nm.
- a structure of Fe/MgGa 2 O 4 (3.0 nm)/Mg (0.6 nm)/Fe/Cr is provided in the first sample.
- the preparation conditions of the first sample are as follows.
- a Cr layer is formed by sputtering at room temperature on a substrate (not illustrated); subsequently, heat treatment is performed at 800° C.
- An Fe layer is formed by sputtering at room temperature on the Cr layer; subsequently, heat treatment is performed at 400 ° C.
- a Mg layer is formed by sputtering at room temperature on the Fe layer; and a MgGa 2 O 4 layer is formed by sputtering at room temperature on the Mg layer.
- heat treatment is performed at 500 ° C.
- An Fe layer is formed by sputtering at room temperature on the MgGa 2 O 4 layer; subsequently, heat treatment is performed at 400 ° C.
- the first sample is made.
- FIG. 2 is a graph illustrating a characteristic of the magnetoresistive element according to the embodiment.
- the horizontal axis of FIG. 2 is an external magnetic field Ha (oersteds (Oe)) applied from the outside to the first sample SP 1 (the magnetoresistive element 110 A) recited above.
- the vertical axis is a magnetoresistance ratio MR 1 (%).
- the measurement temperature of the magnetoresistance ratio MR 1 is 300 K (Kelvin).
- the magnetoresistance ratio MR 1 (at room temperature) is about 121% and is high. For example, this suggests that the coherent tunneling effect arises in the first sample SP 1 .
- the sample of this structural analysis has the structure of the first sample SP 1 in which the Mg layer is not provided.
- the sample of the structure analysis has the structure of the magnetoresistive element 110 illustrated in FIG. 1A .
- the sample of the structure analysis is similar to the first sample SP 1 .
- FIG. 3A to FIG. 3E are photographs illustrating the analysis results of the magnetoresistive element.
- FIG. 3A is a cross sectional STEM (Scanning Transmission Electron Microscope) image of the sample. The image is observed along the Fe [110] plane.
- FIG. 3B to FIG. 3D show the analysis results of energy dispersive X-ray spectroscopy (EDS).
- FIG. 3B to FIG. 3D correspond respectively to the distributions of Mg, Ga, and O.
- FIG. 3E shows a nano electron diffraction image of the sample. The image is acquired from the region at the vicinity of the first nonmagnetic layer 11 N (the MgGa 2 O 4 layer) inside the sample.
- the numerals shown in FIG. 3E show the crystal planes of the diffraction spots.
- the interface of the MgGa 2 O 4 layer is exceedingly flat. It is considered that the stacked structure inside the sample is formed by epitaxial growth with the (001) orientation.
- the MgGa 2 O 4 layer has, for example, a cubic inverse-spinel structure.
- the MgGa 2 O 4 layer may be slightly tetragonally distorted. It is considered that this is due to the effect of the stress generated in the stacked structure including the MgGa 2 O 4 layer. Dislocations substantially are not formed in the MgGa 2 O 4 layer of the sample. A lattice-matched interface is obtained.
- the MgGa 2 O 4 layer is uniform. Segregation or elemental interdiffusion at the interfaces is not observed. It can be seen from the RBS analysis results that the MgGa 2 O 4 layer has a substantially stoichiometric composition.
- the stacked structure of the sample has the epitaxial relationship of Fe (001) [110]//MgGa 2 O 4 (001) [100]. ⁇ 022 ⁇ spots of MgGa 2 O 4 exist in FIG. 3E . Therefore, this suggests that the MgGa 2 O 4 is ordered in a spinel structure.
- the spinel structure includes a normal spinel structure or an inverse-spinel structure.
- the spinel structure includes an inverse-spinel structure in the sample recited above.
- FIG. 4A and FIG. 4B are graphs illustrating analysis results of the magnetoresistive element.
- FIG. 1B show examples of XANES (X-ray absorption near edge structure) analysis results of second to fourth samples SP 2 to SP 4 .
- the second to fourth samples SP 2 to SP 4 have configurations similar to that of the first sample SP 1 recited above (the structure of the magnetoresistive element 110 A illustrated in FIG. 1B ).
- the first nonmagnetic layer thickness t 1 of the MgGa 2 O 4 layer (the first nonmagnetic layer 11 N) is different between the second to fourth samples SP 2 to SP 4 .
- the first nonmagnetic layer thickness t 1 is 2.8 nm, 1.9 nm, and 1.1 nm respectively in the second to fourth samples SP 2 to SP 4 .
- the binding state of Ga is focused upon in the analysis results.
- FIG. 4B is an enlarged view of a portion of FIG. 4A .
- the horizontal axis is a photon energy Ep (eV).
- the vertical axis is an intensity Int.
- the intensity Int is displayed as being normalized.
- heat treatment at 400 ° C. is performed after forming the Mg layer and the MgGa 2 O 4 layer by sputtering at room temperature.
- the second to fourth samples SP 2 to SP 4 are made using conditions similar to those of the first sample SP 1 .
- peaks are obtained in a range of the photon energy Ep not less than 10370 eV (electron volts) and not more than 10385 eV.
- the peaks are related to the binding state of Ga.
- the peaks correspond to the peaks of the photon energy Ep corresponding to the electron energy of the Ga—K shell.
- the first nonmagnetic layer thickness t 1 is 1.1 nm
- two peaks are observed distinctly in the range of the photon energy Ep.
- One of the two peaks corresponds to the peak when the Ga exists in a tetrahedral configuration (a first state).
- the other one of the two peaks corresponds to the peak when the Ga exists in an octahedral configuration (a second state).
- the two peaks are observed for the fourth sample SP 4 in which the first nonmagnetic layer thickness t 1 is 1.1 nm. It is estimated that the first state and the second state recited above exist in the fourth sample SP 4 .
- a valley is observed between the two peaks. The intensity Int at the valley is lower than the intensities Int at the two peaks.
- the intensities Int of the two peaks are substantially the same.
- the amount (the density) of Ga at the tetrahedral sites and the amount (the density) of Ga at the octahedral sites are the same. Therefore, in the sample in which the first nonmagnetic layer thickness t 1 is 1.1 nm, it is estimated that a substantially perfect inverse-spinel structure is provided.
- the peak on the low-energy side has a shoulder-like shape.
- the intensity Int of the peak on the low-energy side relatively increases as the first nonmagnetic layer thickness t 1 decreases. This suggests an increase of the spinel inversion degree.
- the inverse-spinel structure exists.
- the peak on the low-energy side has a shoulder-like shape as well, the shoulder originates in the inverse-spinel structure.
- the inverse-spinel structure is included for the shoulder-like shape as well.
- the oxide included in the first nonmagnetic layer 11 N includes Ga; and the oxide has multiple photon energy peaks corresponding to the binding state of the Ga included in the oxide in X-ray absorption near edge structure analysis.
- the oxide in the X-ray absorption near edge structure analysis, the oxide has multiple photon energy peaks corresponding to the electron energy of the Ga—K shell included in the oxide.
- the oxide included in the first nonmagnetic layer 11 N includes Mg, Ga, and oxygen
- the oxide has two peak intensities and an intermediate intensity (a valley) between the two peaks in the range of the photon energy Ep of not less than 10370 eV and not more than 10385 eV in XANES analysis.
- One of the two peak intensities is a first peak intensity of a first photon energy (in the example, not less than 10373 eV and but than 17376 eV).
- the other one of the two peak intensities is a second peak intensity of a second photon energy (in the example, greater than 10376 eV and not more than 10385 eV).
- the second photon energy is larger than the first photon energy.
- the intermediate intensity is an intensity corresponding to a third photon energy.
- the third photon energy is between the first photon energy and the second photon energy.
- the intermediate intensity of the third photon energy is lower than the first peak intensity and lower than the second peak intensity.
- the first nonmagnetic layer 11 N includes the inverse-spinel structure if at least such an intermediate intensity (valley) is observed.
- the first nonmagnetic layer 11 N (the MgGa 2 O 4 layer) includes the inverse-spinel structure in the sample illustrated in FIG. 3A to FIG. 3E as well. The shoulder recited above is observed.
- heat treatment is performed after the film deposition of each layer.
- the state of the crystal of the first nonmagnetic layer 11 N changes according to the conditions of the heat treatment. For example, the state of the crystal changes according to the temperature, time, etc., of the heat treatment. The state of the crystal changes also according to the rising curve, the cooling curve, etc., of the temperature of the heat treatment.
- the oxide that includes the inverse-spinel structure is obtained by employing the appropriate preparation conditions.
- a thin oxide layer (the first nonmagnetic layer 11 N) that is 4 nm or less is affected easily by the layers adjacent to the oxide layer.
- the thin oxide layer is affected easily by the first magnetic layer 11 or the second magnetic layer 12 .
- the thin oxide layer is affected easily by the second nonmagnetic layer 12 N or the base layer 10 S used as the foundation.
- the inverse-spinel structure can be formed in the thin oxide layer as well.
- the structure (the proportion of normal spinel, inverse spinel, and amorphous) of the layer of MgGa 2 O 4 changes according to the preparation conditions, the thickness, etc.
- the inverse-spinel structure is obtained by using the appropriate preparation conditions and thickness.
- the state of the crystal also changes according to the temperature of the heat treatment, the time of the processing, the temperature change curve (rising and cooling), etc.
- the crystallinity relates also to the oxygen concentration range in the oxygen charging during the heat treatment or after the heat treatment.
- the crystallinity is affected by whether the heat treatment is performed after the formation of each of the multiple layers or whether the heat treatment is performed collectively after the formation of the multiple layers.
- the change of the crystallinity also includes, for example, a portion of Ga 3+ being reduced easily in the metal Ga. If the film deposition rate is high, the crystallinity and the flatness improve; and the inverse-spinel structure is obtained easily. For example, if the thickness is thin, the proportion of the inverse-spinel structure increases. When excessively thin, the film thickness is not more than the critical film thickness of crystallization; and the amorphous proportion increases.
- the thickness of the layer of MgGa 2 O 4 (the first nonmagnetic layer 11 N) is, for example, not less than 1.1 nm and not more than 3.3 nm.
- a spinel-structure oxide is notated (A 1-x B x )[A x B 2-x ]O 4 .
- x is the spinel inversion degree.
- a and B are main group elements or elements of transition metals.
- A is, for example, an element that forms a divalent cation.
- B is an element that forms a trivalent cation.
- O is oxygen.
- the elements inside the “( )”brackets are arranged to occupy 1 ⁇ 8 of the tetrahedral interstices of the cubic lattice formed of the oxygen ions. For example, the arrangement of the elements inside the “( )”brackets is ordered.
- the elements inside the “[ ]” brackets are arranged to occupy 1 ⁇ 2 of the octahedral interstices.
- the arrangement of the elements inside the “[ ]” brackets is ordered.
- the former and the latter each form spinel structures.
- x 0 in a normal spinel structure.
- the normal spinel structure is notated as (A)[B 2 ]O 4 .
- the inverse-spinel structure is notated as (B)[AB]O 4 .
- Typical element metals that are included in the spinel structure include, for example, an element forming a divalent cation and an element forming a trivalent cation.
- the element that forms the divalent cation includes, for example, at least one selected from the group consisting of Zn and Mg.
- the element that forms the trivalent cation includes, for example, at least one selected from the group consisting of In, Ga, and Al.
- the ease of oxygen entering the tetrahedral sites is, for example, (easy) Zn>In>Ga>Mg>Al (difficult).
- In or Ga occupy the tetrahedral sites more easily than does Mg.
- MgGa 2 O 4 and MgIn 2 O 4 include inverse-spinel structures as stable structures.
- rock-salt MgO is used as a tunneling barrier layer (e.g., the first nonmagnetic layer 11 N).
- a high magnetoresistance ratio MR e.g., about 300%) is obtained in the reference example.
- the bandgap of MgO is 7 eV to 8 eV and is high; therefore, the resistance area product is high.
- the thickness of the MgO layer is set to be extremely thin when reducing the element size.
- the insulative properties degrade; and the manufacturing yield or the reliability decreases.
- the oxide according to the embodiment as described below a low resistance area product is obtained. It is considered that this is caused by the small bandgap of the oxide according to the embodiment.
- the bandgap of MgGa 2 O 4 is about 4.7 eV (not less than 4.7 eV and not more than 4.9 eV).
- a high magnetoresistance ratio MR can be obtained while maintaining a low resistance area product.
- the high magnetoresistance ratio MR obtained for a rock-salt MgO case originates in the crystal structure of the rock-salt MgO.
- the Mg is arranged at all of the octahedral sites of oxygen.
- MgGa 2 O 4 i.e., (Ga)[MgGa]O 4
- the inverse-spinel structure is closer to the structure of MgO than is the normal spinel structure.
- the high magnetoresistance ratio MR obtained for MgGa 2 O 4 having the inverse-spinel structure relates to the inverse-spinel structure being closer to the structure of MgO.
- the high MR ratio obtained using the oxide (MgGa 2 O 4 , MgIn 2 O 4 , etc.) of the first nonmagnetic layer 11 N is based on the inverse-spinel structure.
- a low resistance area product RA is obtained for MgGa 2 O 4 and the like.
- MgAl 2 O 4 has a normal spinel structure as a ground state. According to experiments of the inventors of the application, it was found that cation sites are ordered self-organizingly in MgGa 2 O 4 similarly to MgO even by a room-temperature film deposition process. Therefore, the inverse-spinel structure is formed more easily in MgGa 2 O 4 than in MgAl 2 O 4 .
- the layers e.g., the first magnetic layer 11 , etc.
- the first nonmagnetic layer 11 N may be a monocrystal or may be a polycrystal.
- an oriented film is included in the first nonmagnetic layer 11 N.
- the oxide included in the first nonmagnetic layer 11 N is, for example, Mg 1-x Ga x O y (x being greater than 0 and less than 1, and y being not less than 3 and not more than 5).
- the oxide included in the first nonmagnetic layer 11 N is, for example, Mg 1-x In x O y (x being greater than 0 and less than 1, and y being not less than 3 and not more than 5).
- an inverse-spinel structure is obtained for such composition ranges.
- Other examples of the oxide are described below.
- information that relates to the crystalline state of the first nonmagnetic layer 11 N is obtained by a structure analysis method using a TEM (Transmission Electron Microscope).
- TEM Transmission Electron Microscope
- information that relates to the crystal pattern, the existence of lattice defects, the direction of the crystal orientation, etc. is obtained.
- information that relates to the organization structure and the crystal structure in an atomic scale can be obtained by also acquiring the electron diffraction pattern.
- information that relates to whether or not the structure is an inverse-spinel structure is obtained by focusing on designated diffraction spots.
- the information that relates to the crystalline state of the first nonmagnetic layer 11 N is obtained by HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy TEM).
- HAADF-STEM high-angle annular dark-field scanning transmission electron microscopy TEM
- electrons that are irradiated on the atoms and scattered are detected.
- Contrast that is proportional to an atomic number is obtained.
- Information that relates to the atomic arrangement is obtained by focusing on the contrast.
- the information that relates to whether or not the structure is an inverse-spinel structure is obtained.
- the information that relates to the crystalline state of the first nonmagnetic layer 11 N is obtained by XAFS (X-ray absorption fine structure) analysis, EXAFS (Extended X-ray Absorption Fine Structure) analysis, XANES analysis, etc.
- XAFS X-ray absorption fine structure
- EXAFS Extended X-ray Absorption Fine Structure
- XANES Extended X-ray Absorption Fine Structure
- structure analysis and analysis relating to the chemical states are possible.
- non-destructive structure analysis or chemical state analysis in the depth direction is possible by selecting the analysis depth (surface or bulk).
- XANES analysis information that relates to the coordination structure of the elemental components is obtained.
- the information that relates to whether or not the structure is an inverse-spinel structure is obtained.
- the resistance value increases when downscaling is performed. Therefore, it is desirable to reduce the resistance area product RA of the magnetoresistive element.
- MgO or MgAl 2 O 4 is used as the barrier layer (e.g., the first nonmagnetic layer 11 N).
- the decrease of the resistance area product RA as a material is limited; and it is necessary to reduce the thickness of the barrier layer. In the case where the thickness of the barrier layer is reduced, the breakdown voltage of the barrier layer degrades abruptly. Therefore, the improvement of the magnetoresistance ratio MR ratio and the reduction of the resistance area product RA are desirable.
- FIG. 5 is a graph illustrating characteristics of the magnetoresistive element.
- FIG. 5 shows an example of the resistance area product RA for samples (including, for example, the first to fourth samples SP 1 to SP 4 , etc.) in which the first nonmagnetic layer 11 N is MgGa 2 O 4 , and samples (the reference example) in which the first nonmagnetic layer 11 N is MgAl 2 O 4 .
- the first magnetic layer 11 and the second magnetic layer 12 both are Fe layers.
- the horizontal axis of FIG. 5 is the first nonmagnetic layer thickness t 1 (nm).
- the vertical axis is the resistance area product RA ( ⁇ m 2 ).
- the resistance area product RA corresponds to the state in which the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 are in a parallel state.
- the measurement temperature is 300 K.
- the MgGa 2 O 4 includes an inverse-spinel structure.
- the MgAl 2 O 4 includes a normal spinel structure.
- the resistance area product RA of MgGa 2 O 4 is lower than the resistance area product RA of MgAl 2 O 4 .
- Such a characteristic is confirmed at least for the case where the first nonmagnetic layer thickness t 1 is not less than 1.1 nm and not more than 3.3 nm.
- a low resistance area product RA is obtained using the MgGa 2 O 4 (the first nonmagnetic layer 11 N) according to the embodiment.
- a low resistance area product RA is obtained while obtaining a high magnetoresistance ratio MR.
- the first nonmagnetic layer 11 N is not excessively thin.
- high reliability is obtained.
- a high magnetoresistance ratio MR is obtained.
- a low resistance area product RA is obtained. High reliability is obtained
- the change rate (the slope) of the increase of the resistance area product RA for the increase of the thickness in the sample of MgGa 2 O 4 is lower than that of the sample of MgAl 2 O 4 . Therefore, this suggests that the barrier height of the sample of MgGa 2 O 4 is lower than the barrier height of the sample of MgAl 2 O 4 .
- FIG. 6 is a graph illustrating a characteristic of the magnetoresistive element.
- FIG. 6 shows examples of the current density of the two samples shown in FIG. 5 .
- the horizontal axis of FIG. 6 is a bias voltage Vb (volts (V)).
- the vertical axis is a current density CD (A/cm 2 ).
- the measurement temperature is 300 K.
- the solid lines correspond to the state in which the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 are parallel.
- the dotted lines correspond to the state in which the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 are antiparallel.
- the bias voltage Vb at which the current density CD changes abruptly is about 0.6 V.
- the bias voltage Vb at which the current density CD changes abruptly is about 1.1 V.
- the bias voltage Vb at which the current density CD increases abruptly is related to the barrier height. From the results of FIG. 6 , this suggests that the barrier height of MgGa 2 O 4 is lower than the barrier height of MgAl 2 O 4 .
- the barrier height is reduced by reducing the bandgap. For example, by reducing the bandgap, for example, the resistance area product RA is reduced.
- MR ratio magnetoresistance ratio
- the bandgap of MgGa 2 O 4 is estimated to be about 4.7 eV.
- the bandgap of MgGa 2 O 4 is smaller than the bandgap of MgO or MgAl 2 O 4 .
- the barrier height of MgGa 2 O 4 is lower than the barrier height of MgO or MgAl 2 O 4 .
- the resistance area product RA of MgGa 2 O 4 is lower than the resistance area product RA of MgO or MgAl 2 O 4 .
- the bandgap of the oxide included in the first nonmagnetic layer 11 N is favorable for the bandgap of the oxide included in the first nonmagnetic layer 11 N to be, for example, less than 7 eV. It is more favorable for the bandgap of the oxide to be 5 eV or less.
- the bandgap is excessively small, for example, there are cases where it is difficult to maintain the tunneling transport mode and, for example, the MR ratio cannot be sufficiently high.
- the difference between the in-plane lattice constant of the first nonmagnetic layer 11 N and the in-plane lattice constant of the first magnetic layer 11 is favorable for the difference between the in-plane lattice constant of the first nonmagnetic layer 11 N and the in-plane lattice constant of the first magnetic layer 11 to be small, and for the difference between the in-plane lattice constant of the first nonmagnetic layer 11 N and the in-plane lattice constant of the second magnetic layer 12 to be small.
- an interface that has substantially no dislocations is obtained.
- the wave number selectivity of the tunneling electrons is not obstructed.
- a high magnetoresistance ratio MR is obtained.
- the magnetic layers that are included in the magnetoresistive element include, for example, a cubic material having a lattice constant that is about the same as that of Fe.
- the magnetic layers include a tetragonal material having a lattice constant that is about the same as that of MnGa.
- the oxide included in the first nonmagnetic layer 11 N it is favorable for the oxide included in the first nonmagnetic layer 11 N to include a material having good lattice matching with both Fe and MnGa.
- the a-axis lattice constant of Fe is 0.287 nm.
- the lattice constant is 0.405 nm when rotated 45 degrees in the plane.
- the a-axis lattice constant of MnGa is 0.389 nm.
- 1 ⁇ 2 of the lattice constant of the first nonmagnetic layer 11 N is not less than 0.3775 nm and not more than 0.4255 nm.
- the lower limit and the upper limit correspond respectively to 0.755 nm/2 and 0.851 nm/2.
- the first nonmagnetic layer 11 N matches the cubic magnetic layer of Fe and the like with a lattice constant difference within 5%.
- 1 ⁇ 2 of the lattice constant of the first nonmagnetic layer 11 N is not less than 0.370 nm and not more than 0.409 nm.
- the lower limit and the upper limit correspond respectively to 0.740 nm/2 and 0.818 nm/2.
- the first nonmagnetic layer 11 N matches the tetragonal magnetic layer of MnGa and the like with a lattice constant difference within 5%.
- the lattice constants recited above correspond to the lattice constants in one direction in the X-Y plane.
- the oxidation state of the interface is well-controlled by the Mg layer (the second nonmagnetic layer 12 N).
- the second nonmagnetic layer 12 N may be omitted.
- the oxide included in the first nonmagnetic layer 11 N is, for example, crystalline with the ⁇ 100 ⁇ plane and includes divalent cations and trivalent cations.
- the oxide has the inverse-spinel structure as a stable structure.
- the electrical resistance of the magnetoresistive element changes due to energy supplied from the outside such as a write current, etc.
- the change of the electrical resistance is based on the difference of the angles between the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 .
- An example of the energy supplied from the outside is the write current.
- the write current flows to the Z-axis direction.
- the direction of the magnetization of one of the first magnetic layer 11 or the second magnetic layer 12 substantially does not change before and after the supply of the write current to the magnetoresistive element.
- the direction of the other magnetization of the first magnetic layer 11 or the second magnetic layer 12 changes before and after the supply of the write current.
- the former corresponds to the reference layer.
- the latter corresponds to a memory layer (or a free layer).
- the write current is supplied in the direction from the first magnetic layer 11 toward the second magnetic layer 12 in the case where the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 are antiparallel to each other.
- Electrons pass through the first nonmagnetic layer 11 N from the second magnetic layer 12 and flow in the first magnetic layer 11 .
- the electrons are spin-polarized by passing through the second magnetic layer 12 .
- the spin-polarized electrons flow in the first magnetic layer 11 .
- the spin-polarized electrons that have the spin in the same direction as the magnetization of the first magnetic layer 11 pass through the first magnetic layer 11 .
- the spin-polarized electrons that have the spin in the opposite direction of the magnetization of the first magnetic layer 11 apply spin-torque to the magnetization of the first magnetic layer 11 .
- the direction of the magnetization of the first magnetic layer 11 changes to the same orientation as the magnetization of the second magnetic layer 12 .
- the direction of the magnetization of the first magnetic layer 11 reverses.
- the magnetization of the first magnetic layer 11 becomes parallel to (the same direction as) the direction of the magnetization of the second magnetic layer 12 .
- the write current is supplied from the second magnetic layer 12 toward the first magnetic layer 11 .
- the electrons pass through the first nonmagnetic layer 11 N from the first magnetic layer 11 and flow in the second magnetic layer 12 .
- the electrons are spin-polarized by passing through the first magnetic layer 11 .
- the spin-polarized electrons flow in the second magnetic layer 12 .
- the spin-polarized electrons that have the spin in the same direction as the magnetization of the second magnetic layer 12 pass through the second magnetic layer 12 .
- the spin-polarized electrons that have the spin of the opposite orientation of the magnetization of the second magnetic layer 12 are reflected by the interface between the first nonmagnetic layer 11 N and the second magnetic layer 12 , pass through the first nonmagnetic layer 11 N, and flow into the second magnetic layer 12 .
- These electrons apply spin-torque to the magnetization of the first magnetic layer 11 and act to cause the direction of the magnetization of the first magnetic layer 11 to be oriented in the opposite direction of the magnetization of the second magnetic layer 12 .
- the direction of the magnetization of the first magnetic layer 11 reverses.
- the magnetization of the first magnetic layer 11 becomes antiparallel to the direction of the magnetization of the second magnetic layer 12 .
- the first magnetic layer 11 and the second magnetic layer 12 are mutually interchangeable.
- the first magnetic layer 11 may be the reference layer; and the second magnetic layer 12 may be the memory layer.
- the coercivity, an anisotropic magnetic field Hk, or a Gilbert damping constant ⁇ it is favorable for at least one of the coercivity, an anisotropic magnetic field Hk, or a Gilbert damping constant ⁇ to be different between the first magnetic layer 11 and the second magnetic layer 12 ; and, for example, the angle of the magnetization direction can be controlled more stably.
- the magnetic layer in which one of the coercivity, the anisotropic magnetic field Hk, or the Gilbert damping constant ⁇ is relatively large corresponds to the reference layer.
- the magnetic layer in which one of the coercivity, the anisotropic magnetic field Hk, or the Gilbert damping constant ⁇ is relatively small corresponds to the memory layer.
- the magnetoresistive element recited below also includes the first magnetic layer 11 , the second magnetic layer 12 , and the first nonmagnetic layer 11 N.
- the base layer 10 S e.g., a metal layer of Cr, etc.
- the magnetoresistive element is similar to the magnetoresistive element 110 or 110 A; and a description is therefore omitted.
- the second nonmagnetic layer 12 N may be provided in the several examples of the magnetoresistive element described below.
- first element name (second element name) means the state in which the element of the second element name is included in the material of the first element name or the state in which the second element substantially is not included.
- the notation “CoFe(B)” corresponds to the state in which CoFe is included or the state in which CoFeB is included.
- the notation “material name (plane orientation)” means that one surface (a film surface) of a layer of the material name is aligned with the plane orientation.
- the notation “MnGa (001)” corresponds to the state in which a layer of MnGa is stacked with another layer, and one surface of the MnGa is aligned with the (001) plane.
- the one surface crosses a direction (the stacking direction) connecting the layer of MnGa and the other layer.
- the one surface is, for example, a surface aligned with the X-Y plane.
- FIG. 7 is a schematic cross-sectional view showing the other magnetoresistive element according to the first embodiment.
- a third magnetic layer 13 is provided in the other magnetoresistive element 111 according to the embodiment.
- the third magnetic layer 13 is provided between the first magnetic layer 11 and the first nonmagnetic layer 11 N.
- the state in which the first magnetic layer 11 and the third magnetic layer 13 are magnetically coupled to each other is favorable.
- the magnetization of the first magnetic layer 11 reverses as one body with the third magnetic layer 13 .
- the magnetization of the third magnetic layer 13 reverses as one body with the first magnetic layer 11 .
- the orientation of the magnetization of the first magnetic layer 11 is substantially the same as the orientation of the magnetization of the third magnetic layer 13 .
- the spin polarization can be large by using the third magnetic layer 13 .
- the magnetoresistance ratio MR can be increased further.
- the first magnetic layer 11 includes MnGa.
- the third magnetic layer 13 includes CoFe(B).
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa 2 O 4 (001)/CoFe(B) (001)/MnGa (001) is obtained.
- the first magnetic layer 11 includes MnGa.
- the third magnetic layer 13 includes Co 2 FeAl.
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa 2 O 4 (001)/Co 2 FeAl (001)/MnGa (001) is obtained.
- the first magnetic layer 11 includes MnGa.
- the third magnetic layer 13 includes Fe 3 O 4 .
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa 2 O 4 (001)/Fe 3 O 4 (001)/MnGa (001) is obtained.
- FIG. 8 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 A includes the third magnetic layer 13 and a first intermediate layer 21 .
- the third magnetic layer 13 is provided between the first magnetic layer 11 and the first nonmagnetic layer 11 N.
- the first intermediate layer 21 is provided between the first magnetic layer 11 and the third magnetic layer 13 .
- the spin polarization is increased by the third magnetic layer 13 .
- the crystal structure between the first magnetic layer 11 and the third magnetic layer 13 is adjusted by the first intermediate layer 21 .
- the diffusion of the elements is suppressed by the first intermediate layer 21 .
- the first magnetic layer 11 includes MnGa.
- the first intermediate layer 21 includes an amorphous layer.
- the third magnetic layer 13 includes, for example, CoFe(B).
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa 2 O 4 (001)/CoFe(B) (001)/amorphous layer/MnGa (001) is provided.
- the amorphous layer of the first intermediate layer 21 includes, for example, at least one element selected from the group consisting of Mg, Ba, Ca, Sr, Sc, Y, Ta, W, Nb, Gd, Tb, Dy, Ce, Ho, Yb, Er, B, C, and N.
- the first magnetic layer 11 includes MnGa.
- the first intermediate layer 21 includes a crystalline layer.
- the third magnetic layer 13 includes Co 2 FeAl.
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa 2 O 4 (001)/Co 2 FeAl (001)/crystalline layer/MnGa (001) is provided.
- FIG. 9 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 B includes a fourth magnetic layer 14 .
- the fourth magnetic layer 14 is provided between the second magnetic layer 12 and the first nonmagnetic layer 11 N.
- the fourth magnetic layer 14 is magnetically coupled to, for example, the second magnetic layer 12 .
- the spin polarization is increased by providing the fourth magnetic layer 14 .
- the first magnetic layer 11 includes CoFe(B).
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes CoFe(B).
- the second magnetic layer 12 includes MnGe.
- the orientation relationship of MnGe (001)/CoFe(B) (001)/MgGa 2 O 4 (001)/CoFe(B) (001) is provided.
- the first magnetic layer 11 includes Co 2 FeAl.
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes Co 2 FeAl.
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/Co 2 FeAl (001)/MgGa 2 O 4 (001)/Co 2 FeAl (001) is provided.
- FIG. 10 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 C includes the fourth magnetic layer 14 and a second intermediate layer 22 .
- the fourth magnetic layer 14 is provided between the second magnetic layer 12 and the first nonmagnetic layer 11 N.
- the second intermediate layer 22 is provided between the fourth magnetic layer 14 and the second magnetic layer 12 .
- the fourth magnetic layer 14 is magnetically coupled to, for example, the second magnetic layer 12 .
- the spin polarization is increased by providing the fourth magnetic layer 14 .
- the crystal structure between the second magnetic layer 12 and the fourth magnetic layer 14 is adjusted by the second intermediate layer 22 .
- the diffusion of the elements is suppressed by the second intermediate layer 22 .
- the first magnetic layer 11 includes CoFe(B).
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes CoFe(B).
- the second intermediate layer 22 includes an amorphous layer.
- the second magnetic layer 12 includes CoPt.
- the amorphous layer includes, for example, at least one element selected from the group consisting of Ta, W, Mo, Nb, Ru, Rh, and Ir.
- the first magnetic layer 11 includes Co 2 FeAl.
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes Co 2 FeAl.
- the second intermediate layer 22 includes a crystalline layer.
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/crystalline layer/Co 2 FeAl (001)/MgGa 2 O 4 (001)/Co 2 FeAl (001) is provided.
- FIG. 11 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 D includes the third magnetic layer 13 and the fourth magnetic layer 14 .
- the first magnetic layer 11 includes MnGa.
- the third magnetic layer 13 includes CoFe(B).
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes CoFe(B).
- the second magnetic layer 12 includes MnGe.
- the orientation relationship of MnGe (001)/CoFe(B) (001)/MgGa 2 O 4 (001)/CoFe(B) (001)/MnGa (001) is provided.
- the first magnetic layer 11 includes MnGa.
- the third magnetic layer 13 includes Co 2 FeAl.
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes Co 2 FeAl.
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/Co 2 FeAl (001)/MgGa 2 O 4 (001)/Co 2 FeAl (001)/MnGa (001) is provided.
- FIG. 12 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 E includes the first intermediate layer 21 , the third magnetic layer 13 , the fourth magnetic layer 14 , and the second intermediate layer 22 .
- the first magnetic layer 11 includes MnGa.
- the first intermediate layer 21 includes an amorphous layer.
- the third magnetic layer 13 includes CoFe(B).
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes CoFe(B).
- the second intermediate layer 22 includes an amorphous layer.
- the second magnetic layer 12 includes CoPt.
- the orientation relationship of CoPt (111)/amorphous layer/CoFe(B) (001)/MgGa 2 O 4 (001)/CoFe(B) (001)/amorphous layer/MnGa (001) is provided.
- the first magnetic layer 11 includes MnGa.
- the first intermediate layer 21 includes a crystalline layer.
- the third magnetic layer 13 includes Co 2 FeAl.
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer 14 includes Co 2 FeAl.
- the second intermediate layer 22 includes a crystalline layer.
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/crystalline layer/Co 2 FeAl (001)/MgGa 2 O 4 (001)/Co 2 FeAl (001)/crystalline layer/MnGa (001) is provided.
- the first magnetic layer 11 includes MnGa.
- the first intermediate layer 21 includes a crystalline layer.
- the third magnetic layer 13 includes Fe 3 O 4 .
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the fourth magnetic layer includes Co 2 FeAl.
- the second intermediate layer 22 includes a crystalline layer.
- the second magnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/crystalline layer/Co 2 FeAl (001)/MgGa 2 O 4 (001)/Fe 3 O 4 (001)/crystalline layer/MnGa (001) is provided.
- FIG. 13 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 F includes the first magnetic layer 11 , the first nonmagnetic layer 11 N, and the second magnetic layer 12 .
- the first magnetic layer 11 includes CoFe(B).
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the second magnetic layer 12 includes CoFe(B). The orientation relationship of CoFe(B) (001)/MgGa 2 O 4 (001)/CoFe(B) is provided.
- the first magnetic layer 11 includes MnGa.
- the first nonmagnetic layer 11 N includes crystalline MgGa 2 O 4 .
- the second magnetic layer 12 includes MnGe.
- the orientation relationship of MnGe (001)/MgGa 2 O 4 (001)/MnGa (001) is provided.
- FIG. 14 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 G includes the third magnetic layer 13 , the fourth magnetic layer 14 , a third nonmagnetic layer 13 N, and a fifth magnetic layer 15 .
- the second magnetic layer 12 is provided between the first magnetic layer 11 and the fifth magnetic layer 15 .
- the third nonmagnetic layer 13 N is provided between the second magnetic layer 12 and the fifth magnetic layer 15 .
- the third magnetic layer 13 also is provided between the first magnetic layer 11 and the first nonmagnetic layer 11 N.
- the fourth magnetic layer 14 is provided between the second magnetic layer 12 and the first nonmagnetic layer 11 N.
- the fourth magnetic layer 14 and the second magnetic layer 12 are reference layers.
- the third magnetic layer 13 and the first magnetic layer 11 are memory layers.
- the fifth magnetic layer 15 functions as, for example, a bias layer or a shift adjustment layer.
- the magnetization of the fifth magnetic layer 15 is antiparallel to (the opposite orientation of) the orientation of the magnetization of the second magnetic layer 12 .
- the fifth magnetic layer 15 may have antiferromagnetic (synthetic anti-ferromagnetic) coupling to the second magnetic layer 12 via the third nonmagnetic layer 13 N.
- the shift of the current of the magnetization reversal of the memory layer due to the stray magnetic field from the reference layer can be suppressed.
- the shift of the current of the magnetization reversal due to the stray magnetic field can be adjusted.
- the third nonmagnetic layer 13 N it is favorable for the third nonmagnetic layer 13 N to have high heat resistance. For example, thermal mixing between the second magnetic layer 12 and the fifth magnetic layer 15 due to the annealing processes can be suppressed. For example, it is favorable for the third nonmagnetic layer 13 N to have the function of controlling the orientation of the crystal when forming the fifth magnetic layer 15 .
- the third nonmagnetic layer 13 N is excessively thick, the distance between the fifth magnetic layer 15 and the memory layer (in the example, the first magnetic layer 11 , etc.) is longer. Therefore, there are cases where the shift adjustment magnetic field applied to the memory layer from the fifth magnetic layer 15 decreases. It is favorable for the thickness of the third nonmagnetic layer 13 N to be, for example, 5 nm or less. Thereby, the decrease of the shift adjustment magnetic field recited above is suppressed.
- the fifth magnetic layer 15 includes, for example, a ferromagnetic material having an easy magnetization axis in a direction perpendicular to the film face.
- the distance between the fifth magnetic layer 15 and the memory layer is longer than the distance between the reference layer and the memory layer.
- the saturation magnetization of the fifth magnetic layer 15 is higher than the saturation magnetization of the reference layer.
- the thickness of the reference layer is taken as tr; and the saturation magnetization of the reference layer is taken as Msr.
- the thickness of the fifth magnetic layer 15 is taken as t 5 ; and the saturation magnetization of the fifth magnetic layer 15 is taken as Ms 5 .
- the thickness of the second magnetic layer 12 is taken as t 2 ; and the saturation magnetization of the second magnetic layer 12 is taken as Ms 2 .
- the thickness of the fourth magnetic layer 14 is taken as t 4 ; and the saturation magnetization of the fourth magnetic layer 14 is taken as Ms 4 .
- the thickness (tr) of the reference layer is the sum of the thickness (t 4 ) of the fourth magnetic layer 14 and the thickness (t 2 ) of the second magnetic layer 12 .
- the magnetization amount (Msr ⁇ tr) of the reference layer is, for example, (Ms 2 ⁇ t 2 +Ms 4 ⁇ t 4 ).
- the fifth magnetic layer 15 may be provided in combination with any reference layer.
- the reference layer is positioned between the fifth magnetic layer 15 and the memory layer.
- the third nonmagnetic layer 13 N may be provided between the fifth magnetic layer 15 and the reference layer.
- FIG. 15 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 H includes the third magnetic layer 13 , the fourth magnetic layer 14 , and the fifth magnetic layer 15 .
- the first magnetic layer 11 is provided between the fifth magnetic layer 15 and the second magnetic layer 12 .
- the base layer 10 S is provided between the fifth magnetic layer 15 and the first magnetic layer 11 .
- the first nonmagnetic layer 11 N is provided between the first magnetic layer 11 and the second magnetic layer 12 .
- the third magnetic layer 13 is provided between the first magnetic layer 11 and the first nonmagnetic layer 11 N.
- the fourth magnetic layer 14 is provided between the second magnetic layer 12 and the first nonmagnetic layer 11 N.
- the first magnetic layer 11 is used as, for example, a reference layer.
- the second magnetic layer 12 is used as a memory layer.
- FIG. 16 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 I includes the third magnetic layer 13 , the fourth magnetic layer 14 , the fifth magnetic layer 15 , and the third nonmagnetic layer 13 N.
- the fifth magnetic layer 15 is provided between the base layer 10 S and the second magnetic layer 12 .
- the first magnetic layer 11 is provided between the fifth magnetic layer 15 and the second magnetic layer 12 .
- the third nonmagnetic layer 13 N is provided between the fifth magnetic layer 15 and the first magnetic layer 11 .
- the first nonmagnetic layer 11 N is provided between the first magnetic layer 11 and the second magnetic layer 12 .
- the third magnetic layer 13 is provided between the first magnetic layer 11 and the first nonmagnetic layer 11 N.
- the fourth magnetic layer 14 is provided between the second magnetic layer 12 and the first nonmagnetic layer 11 N.
- the first magnetic layer 11 is used as, for example, a reference layer.
- the second magnetic layer 12 is used as a memory layer.
- the strength of the stray magnetic field applied to the memory layer from the fifth magnetic layer 15 may be set to be substantially the same as the strength of the stray magnetic field applied to the memory layer from the reference layer.
- the total magnetization amount of the shift adjustment layer is smaller than the total magnetization amount of the reference layer in the case where the distance between the memory layer and the shift adjustment layer is shorter than the distance between the memory layer and the reference layer.
- the total magnetization amount of the shift adjustment layer is larger than the total magnetization amount of the reference layer.
- the oxide included in the first nonmagnetic layer 11 N includes the inverse-spinel structure. Thereby, a high magnetoresistance ratio MR is obtained. Further, a low resistance area product RA is obtained. High reliability is obtained.
- the orientation of the crystal is controlled for the first magnetic layer 11 and the second magnetic layer 12 .
- the state of being perpendicular to the film face corresponds to the state of being aligned with the Z-axis direction.
- the state of being parallel to the film face corresponds to the state of being aligned with one direction in the X-Y plane.
- the magnetoresistive element according to the embodiment is an in-plane magnetization element (an in-plane magnetization MTJ element) or a perpendicular magnetization element (a perpendicular magnetization MTJ element).
- the in-plane magnetization element for example, the magnetization direction of the first magnetic layer 11 and the magnetization direction of the second magnetic layer 12 are aligned with the film face.
- the perpendicular magnetization element for example, the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 are aligned with a direction perpendicular to the film face.
- the internal energy is lowest when the spontaneous magnetization is oriented in its easy magnetization direction in the state of no external magnetic field.
- the internal energy is largest when the spontaneous magnetization is oriented in its hard magnetization direction in the state in which there is no external magnetic field.
- the first nonmagnetic layer 11 N may not be an epitaxial layer in which the crystal orientation in the in-plane direction is uniform.
- the first nonmagnetic layer 11 N may include an epitaxially grown monocrystal.
- the first nonmagnetic layer 11 N may have a polycrystalline structure having the c-axis orientation.
- the wave number selectivity of the tunneling electrons can be improved.
- a high magnetoresistance ratio MR can be obtained.
- the magnetoresistive elements 111 and 111 A to 111 F recited above it is favorable for the first nonmagnetic layer 11 N to be epitaxially grown. Thereby, the wave number selectivity of the tunneling electrons can be improved. A high magnetoresistance ratio MR is obtained.
- the magnetoresistive elements 111 and 111 E recited above it is favorable for the first nonmagnetic layer 11 N to be epitaxially grown. Thereby, the wave number selectivity of the tunneling electrons can be improved. A high magnetoresistance ratio MR is obtained.
- the oxide included in the first nonmagnetic layer 11 N may include In and oxygen. In such a case as well, the oxide includes the inverse-spinel structure. In the embodiment, the oxide that is included in the first nonmagnetic layer 11 N may include Mg, Ga, In, and oxygen. In such a case as well, the oxide includes the inverse-spinel structure.
- At least one of the first magnetic layer 11 or the second magnetic layer 12 includes at least one selected from the group consisting of Co and Fe.
- at least one of the first magnetic layer 11 or the second magnetic layer 12 includes a first element and a second element.
- the first element is selected from the group consisting of Mn, Al, Ge, and Ga.
- the second element is selected from the group consisting of Mn, Al, Ge, and Ga and is different from the first element recited above.
- At least one of the third magnetic layer 13 or the fourth magnetic layer 14 includes, for example, at least one selected from the group consisting of Co and Fe.
- the base layer 10 S is, for example, a foundation layer.
- the crystallinity of the other layers is controlled by the base layer 10 S.
- the crystallinity includes, for example, the orientation of the crystal, the grain size of the crystal, etc.
- the base layer 10 S is conductive or insulative.
- the base layer 10 S includes a conductive material in the case where a current is caused to flow in the base layer 10 S.
- the base layer 10 S has a NaCl structure having the (001) orientation.
- the base layer 10 S includes a nitride.
- the nitride includes at least one selected from the group consisting of Ti, Zr, Nb, V, Hf, Ta, Mo, W, B, Al, and Ce.
- the base layer 10 S includes a perovskite oxide layer.
- the perovskite oxide layer includes a perovskite oxide having the (002) orientation of ABO 3 .
- the site “A” includes at least one element selected from the group consisting of Sr, Ce, Dy, La, K, Ca, Na, Pb, and Ba.
- the site “B” includes at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Nb, Mo, Ru, Ir, Ta, Ce, and Pb.
- the base layer 10 S includes a layer of an oxide.
- the layer of the oxide has a NaCl structure having the (001) orientation.
- the layer of the oxide includes at least one element selected from the group consisting of Mg, Al, and Ce.
- the base layer 10 S includes a layer including at least one selected from the group consisting of Al, Cr, Ga, Fe, Co, Ni, Rh, Pd, Ag, Ir, Pt, Au, Mo, and W.
- the layer has a tetragonal crystal structure having the (001) orientation. Or, the layer has a cubic crystal structure having the (001) orientation.
- the base layer 10 S has a stacked structure including any of the multiple layers of the first to fourth examples recited above.
- the crystallinities of the other layers can be controlled by the base layer 10 S of the first to fifth examples such as that recited above. Good characteristics are obtained.
- the first magnetic layer 11 has, for example, perpendicular magnetization. For example, a saturation magnetization Ms of the material (the magnetic material) of the first magnetic layer 11 is small.
- the material of the first magnetic layer 11 has, for example, a high magnetic anisotropy energy Ku.
- the material of the first magnetic layer 11 has, for example, a low Gilbert damping constant.
- a high thermal stability is obtained.
- the magnetization reversal is performed using a low current.
- a thermal stability index ⁇ is maintained by the high magnetic anisotropy energy Ku.
- the material of the first magnetic layer 11 it is favorable for the material of the first magnetic layer 11 to have a high polarization.
- the first magnetic layer 11 includes a magnetic layer including at least one selected from the group consisting of Co and Fe.
- the first magnetic layer 11 includes, for example, at least one selected from the group consisting of Co, Fe, CoFe, and CoFeB.
- the first magnetic layer 11 includes a magnetic layer including a Co-based Heusler alloy.
- the Co-based Heusler alloy is notated as Co 2 YZ.
- the first magnetic layer 11 includes at least one selected from the group consisting of Co 2 FeAl, Co 2 MnSi, Co 2 MnGe, Co 2 Mn(Si, Ge), and Co 2 Mn(Ga, Ge).
- the materials and the thicknesses are selected appropriately. Thereby, a perpendicular magnetic anisotropy is obtained in the first magnetic layer 11 .
- the interface-perpendicular magnetic anisotropy is induced markedly by a certain thickness. The characteristics as a perpendicular magnetization film are obtained.
- the magnetic layer that is included in the first magnetic layer 11 includes Mn and a first element.
- the first element includes at least one selected from the group consisting of Al, Ge, and Ga.
- the first magnetic layer 11 includes at least one selected from the group consisting of MnGa, MnAl, MnGe, and MnAlGe.
- the first magnetic layer 11 includes Mn, Ga, and a first element.
- the first element includes at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy.
- the first magnetic layer 11 includes, for example, at least one selected from the group consisting of MnGaAl, MnGaGe, MnGaIr, MnGaCr, MnGaCo, MnGaPt, MnGaRu, MnGaPd, MnGaRh, MnGaNi, MnGaFe, MnGaRe, MnGaAu, MnGaCu, MnGaB, MnGaC, MnGaP, MnGaGd, MnGaTb, and MnGaDy.
- the first magnetic layer 11 is grown so that the c-axis is perpendicular to the film face.
- the first magnetic layer 11 is grown to have the (001) orientation.
- a perpendicular magnetic anisotropy is obtained.
- the base layer 10 S is selected appropriately. Thereby, the crystal orientation growth of the first magnetic layer 11 can be controlled.
- the first magnetic layer 11 includes an alloy.
- the alloy includes a first element and a second element.
- the first element includes, for example, at least one selected from the group consisting of Fe, Co, and Ni.
- the second element includes at least one selected from the group consisting of Ru, Rh, Pd, Ag, Ir, Pt, and Au.
- the first magnetic layer 11 may include a stacked body.
- the stacked body includes, for example, at least one selected from the group consisting of a Co/Pt artificial lattice, a Co/Pd artificial lattice, a Co/Ru artificial lattice, a Co/Ir artificial lattice, and a Co/Au artificial lattice.
- the addition of elements and the ratios of the thicknesses of the magnetic layers and the nonmagnetic layers are adjusted.
- the perpendicular magnetic anisotropy and the saturation magnetization are adjusted.
- the alloy recited above may include, for example, at least one selected from the group consisting of FeRh, FePt, FePd, CoPt, and CoPd.
- the alloy is, for example, a ferromagnetic alloy.
- the first magnetic layer 11 includes an oxide.
- the oxide includes at least one selected from the group consisting of Mn, Co, Ni, Cu, Zn, and Fe.
- the first magnetic layer 11 includes, for example, at least one selected from the group consisting of Fe 3 O 4 , MnFe 2 O 4 , CoFe 2 O 4 , NiFe 2 O 4 , CuFe 2 O 4 , and ZnFe 2 O 4 .
- the first magnetic layer 11 includes, for example, a mixed crystal including at least two selected from the group recited above.
- the group of the materials recited above is, for example, a ferrite having a spinel crystal structure.
- the first magnetic layer 11 has the same crystal symmetry as the first nonmagnetic layer 11 N. Therefore, good matching properties are obtained. For example, an interface that has high crystal quality and high compatibility is obtained. For example, an interface that has substantially no dislocations is obtained.
- magnetite (Fe 3 O 4 ) is a metallic oxide and has half-metallic properties. The Gilbert damping constant of magnetite (Fe 3 O 4 ) is low. Magnetite (Fe 3 O 4 ) is applied particularly favorably to the first magnetic layer 11 .
- the thickness of the first magnetic layer 11 is thin.
- the thickness (the length along the Z-axis direction) of the first magnetic layer 11 is, for example, not less than 1 nm and not more than 5 nm.
- magnetization reversal is obtained using a low current.
- a crystalline material in which a high thermal stability index ⁇ is obtained due to the magneto-crystalline anisotropy there are cases where the anisotropy decreases if the thickness is thin. In the case where such a crystalline material is used, it is favorable for the thickness of the first magnetic layer 11 to be 10 nm or less.
- intermediate magnetic layer refers to at least one of the third magnetic layer 13 or the fourth magnetic layer 14 .
- the intermediate magnetic layer is, for example, a perpendicular magnetization film.
- the intermediate magnetic layer has, for example, a high magnetic anisotropy energy Ku.
- the intermediate magnetic layer has a high polarization.
- a high thermal stability index ⁇ is maintained by the high magnetic anisotropy energy Ku.
- the intermediate magnetic layer functions as the intermediate magnetic layer on the reference layer side, it is favorable for the saturation magnetization of the intermediate magnetic layer to be low. Thereby, the stray magnetic field into the memory layer can be reduced.
- the intermediate magnetic layer functions as the intermediate magnetic layer on the memory layer side, it is favorable for the Gilbert damping constant of the intermediate magnetic layer to be low. Thereby, for example, the magnetization reversal due to the current is easy.
- the intermediate magnetic layer includes an alloy.
- the alloy includes at least one selected from the group consisting of Fe and Co.
- the intermediate magnetic layer may include at least one element selected from the group consisting of Ni, B, C, P, Ta, Ti, Mo, Si, W, Nb, Mn, Al, and Ge.
- the saturation magnetization of the intermediate magnetic layer can be controlled.
- the alloy that is included in the intermediate magnetic layer may include a first element and a second element.
- the first element includes at least one selected from the group consisting of Fe and Co.
- the second element includes at least one selected from the group consisting of Ni, B, C, P, Ta, Ti, Mo, Si, W, Nb, Mn, Al, and Ge.
- the intermediate magnetic layer includes, for example, CoFeB.
- the intermediate magnetic layer may include, for example, at least one selected from the group consisting of CoFeSi, CoFeP, CoFeW, and CoFeNb. These alloys have a spin polarization that is equal to that of CoFeB.
- the intermediate magnetic layer may include, for example, Heusler alloys.
- the Heusler alloys include, for example, at least one selected from the group consisting of Co 2 FeSi, Co 2 MnSi, Co 2 MnGe, Co 2 MnAl, Co 2 FeAl, Co 2 (Fe, Mn) Si, and Co 2 (Fe, Mn) Al.
- the Heusler alloys have, for example, a spin polarization that is equal to or higher than that of CoFeB.
- the Heusler alloys are suited to the intermediate magnetic layer.
- the intermediate magnetic layer includes an oxide.
- the oxide includes at least one selected from the group consisting of Mn, Co, Ni, Cu, Zn, and Fe.
- the intermediate magnetic layer includes, for example, at least one selected from the group consisting of Fe 3 O 4 , MnFe 2 O 4 , CoFe 2 O 4 , NiFe 2 O 4 , CuFe 2 O 4 , and ZnFe 2 O 4 .
- the intermediate magnetic layer may include a mixed crystal including two or more selected from the group of the materials recited above.
- the group of the materials recited above is, for example, a ferrite having a spinel crystal structure.
- the ferrite that has the spinel crystal structure has the same crystal symmetry as the first nonmagnetic layer 11 N.
- the ferrite that has the spinel crystal structure has excellent matching properties.
- high crystal quality is obtained.
- an interface that has substantially no dislocations is obtained.
- Magnetite (Fe 3 O 4 ) is a metallic oxide and has half-metallic properties.
- Magnetite (Fe 3 O 4 ) has a low Gilbert damping constant. Magnetite (Fe 3 O 4 ) is applied particularly favorably to the intermediate magnetic layer.
- the intermediate magnetic layer includes a MnGa alloy.
- the intermediate magnetic layer may further include at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy.
- at least one of the saturation magnetization, the perpendicular magnetic anisotropy, the Gilbert damping constant, or the spin polarization is controlled.
- the intermediate magnetic layer includes, for example, MnGaX.
- the MnGaX includes Mn, Ga, and a first element.
- the first element (X) includes at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy.
- the intermediate magnetic layer includes, for example, at least one selected from the group consisting of MnGaAl, MnGaGe, MnGaIr, MnGaCr, MnGaCo, MnGaPt, MnGaRu, MnGaPd, MnGaRh, MnGaNi, MnGaFe, MnGaRe, MnGaAu, MnGaCu, MnGaB, MnGaC, MnGaP, MnGaGd, MnGaTb, and MnGaDy.
- the intermediate magnetic layer includes a MnGe alloy.
- MnGe alloy for example, in the (001) direction, one state of the spin band is positioned at the Fermi level vicinity. It is considered that the MnGe alloy has half-metallic characteristics for this crystal orientation. For example, the spin polarization of the MnGe alloy can be improved. By applying the MnGe alloy, a high magnetoresistance ratio MR is obtained.
- the intermediate magnetic layer includes an alloy.
- the alloy includes a first element, a second element, and a third element.
- the first element includes at least one selected from the group consisting of Mn, Fe, Co, and Ni.
- the second element includes at least one selected from the group consisting of Zn, Al, Ga, In, Si, Ge, Sn, As, Sb, and Bi.
- the third element includes at least one selected from the group consisting of Zn, Al, Ga, In, Si, Ge, Sn, As, Sb, and Bi.
- the third element is different from the second element.
- the intermediate magnetic layer includes, for example, at least one selected from the group consisting of MnAlGe and MnZnSb.
- the intermediate layer includes a MnAl alloy.
- the MnAl alloy includes a light element.
- the Gilbert damping constant of the MnAl alloy is small. For example, the energy that is necessary for the magnetization reversal is low. For example, the current density necessary for the spin-polarized electrons to reverse the magnetization can be reduced drastically.
- the MnAl alloy has half-metallic characteristics in the (001) direction.
- the MnAl alloy has a high spin polarization. By using the MnAl alloy, for example, a high magnetoresistance ratio MR is obtained.
- the characteristics as a magnetization film are obtained in the appropriate composition range.
- the intermediate magnetic layer is oriented so that the c-axis is perpendicular to the film face.
- the intermediate magnetic layer is grown to have the (001) orientation. Thereby, a perpendicular magnetic anisotropy is obtained.
- the first magnetic layer 11 is selected appropriately.
- the first nonmagnetic layer 11 N is selected appropriately.
- the crystal orientation growth of the intermediate magnetic layer can be controlled by the layer positioned under the intermediate magnetic layer when forming the intermediate magnetic layer.
- the Gilbert damping constant of the magnetic material has a correlation with the magnitude of the spin-orbit coupling of the magnetic material.
- the spin-orbit coupling is large for materials including an element having a large atomic number.
- the Gilbert damping constant is large.
- the magnetic material of the example recited above includes a relatively light element. Therefore, the Gilbert damping constant is small.
- the energy that is necessary for the magnetization reversal is low. For example, the current density necessary for the spin-polarized electrons to reverse the magnetization can be reduced drastically.
- the magnetic material of the example recited above is applicable particularly effectively to the intermediate magnetic layer on the memory layer side.
- the third magnetic layer 13 or the fourth magnetic layer 14 is epitaxially grown from the first nonmagnetic layer 11 N. Thereby, a high magnetoresistance ratio MR is obtained.
- the lattice length along the X-Y plane may be shifted from the unique lattice constant of the material.
- the first nonmagnetic layer 11 N functions as, for example, a tunneling barrier layer.
- the first nonmagnetic layer 11 N is crystalline.
- the first nonmagnetic layer 11 N includes, for example, a monocrystal.
- the first nonmagnetic layer 11 N may include a polycrystal.
- the first nonmagnetic layer 11 N may include an amorphous region.
- the first nonmagnetic layer 11 N includes an oxide.
- the oxide includes Mg and Ga.
- the first nonmagnetic layer 11 N includes, for example, MgGa 2 O 4 .
- the bandgap of MgGa 2 O 4 is about 4.7 eV.
- RA resistance area product
- the lattice constant of MgGa 2 O 4 is 0.8286 nm.
- the lattice mismatch between MgGa 2 O 4 and Fe is about 2.2%.
- the lattice mismatch between MgGa 2 O 4 and MnGa is about 6.4%.
- MgGa 2 O 4 has good lattice matching with many ferromagnetic materials.
- composition ratios of the elements of “MgGa 2 O 4 ” may not be exact.
- the compositions of Mg, Ga, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- MgGa 2 O 4 may not be a perfect cubic crystal.
- tetragonal distortion of 10% or less may be included.
- Fe is used as the first magnetic layer 11 and the second magnetic layer 12 .
- a MgGa 2 O 4 layer is used with the Fe layer, it is considered that a band-folding effect arises because the in-plane lattice constants are different.
- the effective spin polarization of the A band of Fe may decrease due to the band-folding effect. If the decrease of the effective spin polarization is suppressed, a higher magnetoresistance ratio MR is obtained.
- the band-folding effect can be substantially ignored.
- the magnetic layer is a half-metallic Heusler alloy, etc., it is considered that a magnetoresistance ratio MR that is even higher than the magnetoresistance ratio MR of the experimental results described in reference to FIG. 2 is obtained.
- the magnetic layers (the first to fourth magnetic layers 11 to 14 , etc.) that are in directly contact with the first nonmagnetic layer 11 N to include Heusler alloys.
- the oxide included in the first nonmagnetic layer 11 N includes Mg, Ga, and In.
- the first nonmagnetic layer 11 N includes, for example, Mg(Ga, In) 2 O 4 , etc.
- compositions of the elements of “Mg(Ga, In) 2 O 4 ” may not be exact.
- the compositions of Mg, Ga, In, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- the spinel inversion degree is high for MgGa 2 O 4 and MgIn 2 O 4 .
- the first nonmagnetic layer 11 N may include MgGa 2 O 4 (the main material) and In. In has a low melting point and a large ionic radius. By using such In, the spinel inversion degree can be increased.
- the bandgap of MgIn 2 O 4 is smaller than the bandgap of MgGa 2 O 4 .
- the first nonmagnetic layer 11 N may include MgGa 2 O 4 (the main material) and In.
- a small bandgap is obtained. It is favorable for the oxide of the first nonmagnetic layer 11 N to include Mg, Ga, and In. The inverse-spinel structure is more stable; and a small bandgap is obtained.
- the oxide included in the first nonmagnetic layer 11 N includes In.
- the first nonmagnetic layer 11 N includes, for example, at least one selected from the group consisting of MgIn 2 O 4 , ZnIn 2 O 4 , and (Mg, Zn)In 2 O 4 .
- compositions of the elements of “MgIn 2 O 4 ” recited above may not be exact.
- the compositions of Mg, In, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- a main group element metal may be further included in the material of the first nonmagnetic layer 11 N described in reference to the first to third examples recited above.
- the main group element is an element that forms a spinel structure.
- the content of the main group element is, for example, 10 atm % (atomic percent) or less.
- the inverse-spinel structure substantially does not degrade.
- Such a main group element metal includes, for example, at least one selected from the group consisting of Zn, Cd, Al, Si, Ge, and Sn.
- a portion of the elements included in the inverse-spinel structure may be replaced with such a main group metal element. For example, the bandgap, the phase stability, and the lattice constant are adjusted.
- the first nonmagnetic layer 11 N includes two or more layers of the materials described in reference to the first to third examples recited above. These layers are stacked.
- the first layer that is included in the stacked structure contacts, for example, the magnetic layer (the first to fourth magnetic layers 11 to 14 , etc.).
- the second layer that is included in the stacked structure does not contact a magnetic layer.
- the lattice matching of the first layer with the magnetic layer recited above is good.
- the bandgap of the second layer is low.
- the first nonmagnetic layer 11 N includes, for example, at least one selected from the group consisting of MgIn 2 O 4 /MgGa 2 O 4 , Mg(Ga, In) 2 O 4 /MgGa 2 O 4 , MgGa 2 O 4 /MgIn 2 O 4 /MgGa 2 O 4 , and MgGa 2 O 4 /Mg(Ga, In) 2 O 4 /MgGa 2 O 4 .
- compositions of the elements of “AB 2 O 4 ” recited above may not be exact.
- the compositions of the elements of A, B, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- the first nonmagnetic layer 11 N includes a first compound layer and a first layer.
- the first compound layer is one of MgO or MgAl 2 O 4 .
- the first layer is stacked with the first compound layer.
- the first layer includes the materials described in reference to the first to third examples recited above.
- the first compound layer contacts, for example, a magnetic layer (the first to fourth magnetic layers 11 to 14 , etc.).
- the first layer does not contact a magnetic layer.
- a high magnetoresistance ratio MR and a low resistance area product RA are obtained.
- a high magnetoresistance ratio MR is obtained.
- the first nonmagnetic layer 11 N includes, for example, at least one selected from the group consisting of MgGa 2 O 4 /MgO, MgGa 2 O 4 /MgAl 2 O 4 , MgO/MgGa 2 O 4 /MgO, MgAl 2 O 4 /MgGa 2 O 4 /MgAl 2 O 4 , MgIn 2 O 4 /MgO, MgIn 2 O 4 /MgAl 2 O 4 , MgO/MgIn 2 O 4 /MgO, MgAl 2 O 4 /MgIn 2 O 4 /MgAl 2 O 4 , Mg(Ga, In) 2 O 4 /MgO, Mg(Ga, In) 2 O 4 /MgO, Mg(Ga, In) 2 O 4 /MgAl 2 O 4 , MgO/Mg(Ga, In) 2 O 4 /MgAl 2 O 4 , Mg
- compositions of the elements of “MgO” recited above may not be exact.
- the compositions of the elements of Mg and O may be adjusted in the ranges in which the rock-salt structure can be maintained.
- the compositions of the elements of “AB 2 O 4 ” recited above may not be exact.
- the compositions of the elements A, B, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- the second magnetic layer 12 has, for example, a perpendicular magnetization.
- the second magnetic layer 12 has, for example, a high magnetic anisotropy energy Ku.
- the second magnetic layer 12 has, for example, at least one of a coercivity that is larger than the coercivity of the first magnetic layer 11 , an anisotropic magnetic field that is larger than the anisotropic magnetic field of the first magnetic layer 11 , or a Gilbert damping constant that is larger than the Gilbert damping constant of the first magnetic layer 11 .
- the thermal stability index ⁇ can be maintained by the high magnetic anisotropy energy Ku.
- the saturation magnetization Ms of the second magnetic layer 12 can be small. Thereby, for example, the effects of the stray magnetic field from the reference layer can be reduced.
- It is favorable for the polarization of the second magnetic layer 12 to be high. Thereby, for example, a high magnetoresistance ratio MR is obtained.
- the second magnetic layer 12 includes Mn and a first element.
- the first element includes at least one selected from Al, Ge, and Ga.
- the second magnetic layer 12 includes at least one selected from the group consisting of MnGa, MnAl, MnGe, and MnAlGe.
- the second magnetic layer 12 includes Mn, Ga, and a first element.
- the first element includes at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy.
- the second magnetic layer 12 includes, for example, at least one selected from the group consisting of MnGaAl, MnGaGe, MnGaIr, MnGaCr, MnGaCo, MnGaPt, MnGaRu, MnGaPd, MnGaRh, MnGaNi, MnGaFe, MnGaRe, MnGaAu, MnGaCu, MnGaB, MnGaC, MnGaP, MnGaGd, MnGaTb, and MnGaDy.
- the crystal orientation growth of the second magnetic layer 12 can be controlled.
- the c-axis is in a direction perpendicular to the film face.
- growth in the (001) orientation is obtained.
- a perpendicular magnetic anisotropy is obtained.
- the second magnetic layer 12 includes an alloy.
- the crystal of at least a portion of the alloy is oriented in, for example, (111) of a face-centered cubic structure (FCC). Or, the crystal of at least a portion of the alloy is oriented in (0001) of a hexagonal close-packed structure (HCP).
- the alloy that is included in the second magnetic layer 12 may form, for example, an artificial lattice.
- the alloy recited above that has the crystal orientation of (111) of FCC or (0001) of HCP includes, for example, a first element and a second element.
- the first element includes at least one selected from the group consisting of Fe, Co, Ni, and Cu.
- the second element includes at least one selected from the group consisting of Pt, Pd, Rh, and Au.
- the alloy that is included in the second magnetic layer 12 is, for example, a ferromagnetic alloy.
- the ferromagnetic alloy includes, for example, at least one selected from the group consisting of CoPd, CoPt, NiCo, and NiPt.
- the alloy recited above that is included in the second magnetic layer 12 and may form the artificial lattice includes, for example, a first layer and a second layer stacked alternately.
- the first layer includes, for example, an alloy (a ferromagnetic film) including one element selected from the group consisting of Fe, Co, and Ni.
- the second layer includes, for example, an alloy (a nonmagnetic film) including one element selected from the group consisting of Cr, Pt, Pd, Jr, Rh, Ru, Os, Re, Au, and Cu.
- the second magnetic layer 12 includes, for example, at least one selected from the group consisting of a Co/Pt artificial lattice, a Co/Pd artificial lattice, a CoCr/Pt artificial lattice, a Co/Ru artificial lattice, a Co/Ir artificial lattice, a Co/Os artificial lattice, a Co/Au artificial lattice, and a Ni/Cu artificial lattice.
- these artificial lattices at least one of the addition of an element to the ferromagnetic film or the ratio of the thicknesses of the ferromagnetic film and the nonmagnetic film is adjusted.
- At least one of the perpendicular magnetic anisotropy or the saturation magnetization can be adjusted.
- the second magnetic layer 12 includes an alloy.
- the alloy includes a first element and a second element.
- the first element includes at least one selected from the group consisting of Fe, Co, and Ni.
- the first element is, for example, a transition metal.
- the second element includes, for example, at least one selected from the group consisting of Tb, Dy, and Gd.
- the second element is, for example, a rare-earth metal.
- the second magnetic layer 12 includes, for example, at least one selected from the group consisting of TbFe, TbCo, TbFeCo, DyTbFeCo, and GdTbCo.
- the second magnetic layer 12 may include a stacked body. The stacked body includes multiple layers.
- the second magnetic layer 12 may include, for example, at least one stacked body selected from the group consisting of TbFe/Co, TbCo/Fe, TbFeCo/CoFe, DyFe/Co, DyCo/Fe, and DyFeCo/CoFe.
- at least one of the thickness or the composition is adjusted for these alloys.
- at least one of the perpendicular magnetic anisotropy or the saturation magnetization is adjusted.
- the second magnetic layer 12 includes an alloy.
- the alloy includes a first element and a second element.
- the first element includes at least one selected from the group consisting of Fe, Co, Ni, and Cu.
- the second element includes at least one selected from the group consisting of Pt, Pd, Rh, and Au.
- the second magnetic layer 12 includes, for example, a ferromagnetic alloy.
- the ferromagnetic alloy includes at least one selected from the group consisting of FeRh, FePt, FePd, CoPt, and CoPd.
- first intermediate layer 21 and the second intermediate layer 22 will now be described. Hereinbelow, these layers are called the “intermediate layer” for convenience.
- the “intermediate layer” refers to at least one of the first intermediate layer 21 or the second intermediate layer 22 . It is favorable for the intermediate layer to include a nonmagnetic material.
- mixing due to the element diffusion between the first magnetic layer 11 and the third magnetic layer 13 is suppressed by the intermediate layer.
- mixing due to the element diffusion between the second magnetic layer 12 and the fourth magnetic layer 14 is suppressed by the intermediate layer.
- the elements that are included in the intermediate layer and the elements that are included in the magnetic layer may not form a solid solution with each other.
- the elements that are included in the intermediate layer and the elements that are included in the magnetic layer may form a substantially completely intermetallic compound.
- the mixing is suppressed.
- a better effect of repelling hetero elements occurs in the intermediate layer.
- diffusion is suppressed in the intermediate layer.
- the nonmagnetic layer that is included in the intermediate layer may include at least one element selected from the group consisting of Mg, Ba, Ca, Sr, Sc, Y, Ta, W, Nb, Gd, Tb, Dy, Ce, Ho, Yb, Er, B, C, and N.
- the intermediate layer may include a compound including the elements recited above.
- the melting point is increased by the compound.
- the intermediate layer includes at least one selected from the group consisting of a boride including the elements recited above, a carbide including the elements recited above, and a nitride including the elements recited above.
- the intermediate layer may include a stacked body.
- the stacked body includes multiple layers including the elements recited above.
- the stacked body includes multiple layers including the compounds recited above.
- the intermediate layer is provided between two layers and the crystal structures of the two layers are similar to each other, it is favorable for the intermediate layer to be crystalline. For example, it is favorable for the compatibility of the crystal type and the lattice constant of the intermediate layer with the two layers to be good. Thereby, for example, the function of the intermediate layer as a lattice buffer layer increases.
- the intermediate layer is provided between two layers and the crystal structures of the two layers are different from each other, it is favorable for the intermediate layer to have an amorphous state.
- the intermediate layer having an amorphous state for example, the desired orientation state is easier to obtain in at least one of the two layers.
- amorphous state of the intermediate layer for example, there is no long range order (periodic structure) such as that of a crystal.
- the amorphous state of the intermediate layer may have short range order.
- the amorphous state of the intermediate layer may include a polycrystal having an average crystal grain of 2 nm or less.
- the thickness of the intermediate layer is, for example, not less than 0.1 nm and not more than 2 nm.
- the thickness is 0.1 nm or more, the suppression of the element diffusion in the two layers having the intermediate layer interposed is obtained effectively.
- the thickness is 2 nm or less, for example, the magnetic coupling of the two layers having the intermediate layer interposed is maintained.
- a vapor phase epitaxy process is used in at least a portion of the formation of, for example, the oxide included in the first nonmagnetic layer 11 N.
- the vapor phase epitaxy process includes, for example, at least one of sputtering, MBE, or laser ablation.
- the oxide layer is formed by various oxidation processes.
- the oxidation processes include, for example, the flow of an oxygen gas.
- the oxidation processes may include, for example, at least one of a plasma oxidation process or a radical oxidation process.
- a temperature, a processing time, and a power that are suited to the material and thickness of the alloy layer used to form the first nonmagnetic layer 11 N are applied.
- the formation of a film is performed using an oxide target.
- the second manufacturing method is suitable in the case where the differences of the oxidizing capabilities and the melting points are large for the element of “A” and the element of “B” included in the spinel-structure oxide (e.g., AB 2 O 4 ).
- at least one of heating film formation or post-heating may be implemented.
- the first nonmagnetic layer 11 N that has a higher crystallinity is obtained.
- the oxide included in the first nonmagnetic layer 11 N (e.g., MgGa 2 O 4 ) is formed by, for example, sputtering at room temperature. Subsequently, heat treatment is performed at, for example, not less than 300° C. and not more than 600° C. The temperature of the heat treatment may be not less than 400° C. and not more than 500° C. By the heat treatment, high crystallinity and good flatness are obtained. Oxygen may desorb due to the heat treatment. For example, an oxygen gas, etc., may be introduced in the heat treatment or after the heat treatment. Thereby, the desorption of the oxygen can be suppressed.
- an oxygen gas, etc. may be introduced in the heat treatment or after the heat treatment.
- the embodiment relates to a magnetic memory device.
- FIG. 17 is a schematic cross-sectional view illustrating the magnetic memory device according to the second embodiment.
- the magnetic memory device 210 includes, for example, a control element 75 and the magnetoresistive element according to the first embodiment. Any magnetoresistive element according to the first embodiment or any magnetoresistive element of a modification according to the first embodiment may be used. In the example, the magnetoresistive element 111 is used.
- the control element 75 is electrically connected to the magnetoresistive element 111 .
- the control element 75 includes a transistor 70 T.
- a first conductive layer 11 E and a second conductive layer 12 E are provided in the example. These conductive layers are, for example, electrodes. The first magnetic layer 11 , the second magnetic layer 12 , and the first nonmagnetic layer 11 N are provided between these conductive layers. The first conductive layer 11 E is electrically connected to the first magnetic layer 11 . The second conductive layer 12 E is electrically connected to the second magnetic layer 12 .
- a first interconnect 70 a and a second interconnect 70 b are provided in the example.
- the first interconnect 70 a is electrically connected to the first magnetic layer 11 (in the example, the first conductive layer 11 E).
- the second interconnect 70 b is electrically connected to the second magnetic layer 12 (in the example, the second conductive layer 12 E).
- the second interconnect 70 b is one bit line.
- a drain 70 Td of the transistor 70 T is electrically connected to the first interconnect 70 a via a connection portion 78 a.
- a source 70 Ts of the transistor 70 T is electrically connected to another interconnect 78 c via a connection portion 78 b.
- the other interconnect 78 c is, for example, another bit line.
- a gate 70 Tg of the transistor 70 T corresponds to a word line.
- the transistor 70 T is provided in a portion of a semiconductor substrate 70 S.
- the transistor 70 T functions as, for example, a selection transistor.
- An inter-layer insulating portion 701 is provided around the transistor 70 T, the interconnects, the connection portions, etc.
- At least one of the interconnect, the conductive layer, or the connection portion recited above includes, for example, at least one selected from the group consisting of W, Al, AlCu, and Cu.
- multiple magnetoresistive elements 111 are provided.
- One control element 75 is electrically connected to one of the multiple magnetoresistive elements 111 .
- the one of the multiple magnetoresistive elements 111 is selected by the control element 75 .
- the manufacturing method of the example recited below includes a bonding process.
- FIG. 18A to FIG. 18E are schematic cross-sectional views illustrating the method for manufacturing the magnetic memory device according to the second embodiment.
- a first stacked body SB 1 is prepared as shown in FIG. 18A .
- the first stacked body SB 1 includes any magnetoresistive element according to the first embodiment.
- the magnetoresistive element 111 is provided in the example.
- the magnetoresistive element 111 is provided on a substrate 25 in the example.
- the first substrate 25 is a monocrystalline substrate of silicon.
- a first bonding layer 25 a is provided on the magnetoresistive element 111 .
- the layers that are included in the magnetoresistive element 111 are formed on the substrate 25 .
- the formation includes, for example, implementing at least one of sputtering or MBE (Molecular Beam Epitaxy).
- MBE Molecular Beam Epitaxy
- the appropriate conditions are applied to the magnetoresistive element 111 .
- crystallinity that reflects the silicon monocrystal crystallinity of the substrate 25 may be provided in the layers included in the magnetoresistive element 111 .
- at least one layer included in the magnetoresistive element 111 is caused to be substantially monocrystalline.
- a second stacked body SB 2 is prepared as shown in FIG. 18B .
- the second stacked body SB 2 includes, for example, the semiconductor substrate 70 S, the transistor 70 T, the connection portions (referring to FIG. 17 ), the inter-layer insulating portion 701 , and a second bonding layer 25 b.
- the second bonding layer 25 b is provided on the transistor 70 T, the connection portions, and the inter-layer insulating portion 701 .
- the first bonding layer 25 a and the second bonding layer 25 b include metals.
- the metals include, for example, at least one selected from the group consisting of Al, Au, Cu, Ti, and Ta.
- the first bonding layer 25 a and the second bonding layer 25 b are caused to oppose each other. For example, at least one of heating or the application of pressure is performed. The first bonding layer 25 a and the second bonding layer 25 b are bonded to each other.
- a portion of the substrate 25 is removed as shown in FIG. 18D .
- BSG Back Side Grinder
- the thickness of the substrate 25 is reduced.
- the remaining portion of the substrate 25 is removed as shown in FIG. 18E .
- CMP Chemical Mechanical Polishing
- the interconnects, etc. are formed; and the magnetic memory device 210 is made.
- the first stacked body SB 1 that includes the magnetoresistive element 111 and the second stacked body SB 2 that includes the transistor 70 T (the control element 75 ) are prepared separately. These stacked bodies are bonded. Therefore, the appropriate conditions (including the conditions relating to heat) are applied to each of the two stacked bodies. Thereby, good characteristics are obtained for the elements (the magnetoresistive element 111 , the transistor 70 T, etc.) included in each of the stacked bodies. For example, good crystallinity is obtained for the layers. For example, good amorphousness is obtained for the layers.
- FIG. 19 is a schematic view illustrating the magnetic memory device according to the second embodiment.
- the magnetic memory device 220 includes, for example, a controller 70 and the magnetoresistive element according to the first embodiment. Any magnetoresistive element according to the first embodiment or any magnetoresistive element of a modification according to the first embodiment may be used. In the example, the magnetoresistive element 110 is used.
- the controller 70 is electrically connected to the magnetoresistive element 110 .
- the first interconnect 70 a electrically connects the controller 70 and the first magnetic layer 11 (in the example, the first conductive layer 11 E) to each other.
- the second interconnect 70 b electrically connects the controller 70 and the second magnetic layer 12 (in the example, the second conductive layer 12 E) to each other.
- the control element 75 described above may be provided on the path of the electrical connection.
- the controller 70 can sense a value (e.g., at least one of a current, a voltage, or a resistance) corresponding to the electrical resistance of the magnetoresistive element 110 .
- the controller 70 reads information stored in the magnetoresistive element 110 .
- the controller 70 implements, for example, a read operation.
- the controller 70 may apply external energy (a current, a voltage, an electric field, a magnetic field, etc.) to the magnetoresistive element 110 .
- External energy a current, a voltage, an electric field, a magnetic field, etc.
- Multiple states may be formed in the magnetoresistive element 110 by the external energy.
- the electrical resistance of the magnetoresistive element 110 is different between the multiple states.
- the multiple states correspond to the information that is stored. For example, a write operation and an erase operation may be implemented.
- FIG. 20 is a schematic view illustrating a magnetic memory device according to the second embodiment.
- the magnetic memory device 230 includes multiple memory cells MC and the controller 70 .
- One of the multiple memory cells MC includes at least one magnetoresistive element and at least one control element 75 .
- the at least one magnetoresistive element is any magnetoresistive element or a modification of a magnetoresistive element according to the first embodiment.
- the magnetoresistive element 110 is provided in the example.
- a first terminal of the control element 75 is electrically connected to one end of the magnetoresistive element 110 .
- the control element 75 corresponds to, for example, the transistor 70 T.
- the first terminal corresponds to, for example, the drain 70 Td of the transistor 70 T.
- Multiple bit lines BL 1 , multiple bit lines BL 2 , and multiple word lines WL are provided.
- the multiple bit lines BL 1 and BL 2 extend in the Y-axis direction.
- the multiple bit lines BL 1 and BL 2 are arranged in the X-axis direction.
- the multiple word lines WL extend in the X-axis direction.
- the multiple word lines WL are arranged in the Y-axis direction.
- the other end of the magnetoresistive element 110 included in the one of the multiple memory cells MC is electrically connected to one of the multiple bit lines BL 1 .
- a second terminal of the control element 75 included in the one of the multiple memory cells MC is electrically connected to one of the multiple bit lines BL 2 .
- the second terminal corresponds to, for example, the source 70 Ts of the transistor 70 T.
- a third terminal of the control element 75 included in the one of the multiple memory cells MC is electrically connected to one of the multiple word lines WL.
- the third terminal of the control element 75 is electrically connected.
- the third terminal corresponds to, for example, the gate 70 Tg of the transistor 70 T.
- Each of the multiple bit lines BL 1 is connected to a first current source/sink circuit SSC 1 via a first switch SW 1 .
- Each of the multiple bit lines BL 2 is connected to a second current source/sink circuit SSC 2 via a second switch SW 2 .
- the other end of each of the multiple bit lines BL 2 is electrically connected to a read circuit RC.
- the read circuit RC includes, for example, a read current circuit, a sense amplifier, etc.
- the read circuit RC may be electrically connected to each of the multiple bit lines BL 1 .
- the first current source/sink circuit SSC 1 supplies a write current Iw to the multiple bit lines BL 1 .
- the first current source/sink circuit SSC 1 receives the write current Iw from the multiple bit lines BL 1 .
- the second current source/sink circuit SSC 2 supplies the write current Iw to the multiple bit lines BL 2 .
- the second current source/sink circuit SSC 2 receives the write current Iw from the multiple bit lines BL 2 .
- the multiple word lines WL are electrically connected to a row decoder RD.
- the controller 70 may include the control element 75 .
- the first switch SW 1 , the second switch SW 2 , and the control element 75 (the transistor 70 T) that correspond to the selected cell (one of the multiple memory cells MC) are set to the on-state.
- one of the first current source/sink circuit SSC 1 or the second current source/sink circuit SSC 2 functions as a current source.
- the other of the first current source/sink circuit SSC 1 or the second current source/sink circuit SSC 2 functions as a current sink.
- the write current Iw flows in the selected cell in a direction corresponding to the information to be written.
- the write current Iw includes a current pulse.
- the pulse width of the current pulse is, for example, not less than several nanoseconds and not more than several microseconds.
- the write current Iw flows through the magnetoresistive element 110 of the selected cell. For example, spin injection writing is performed by the write current Iw.
- a read current is caused to flow in the magnetoresistive element 110 .
- the magnitude of the read current is smaller than the magnitude of the write current Iw.
- the sense amplifier of the read circuit RC senses a value (at least one of a current or a voltage) corresponding to the electrical resistance of the magnetoresistive element 110 .
- the magnetic memory device 230 is, for example, spin injection-writing magnetic memory.
- FIG. 21 is a schematic view illustrating another magnetic memory device according to the second embodiment.
- the magnetic memory device 240 includes the controller 70 and a magnetoresistive element or a modification of a magnetoresistive element according to the first embodiment.
- the magnetoresistive element 110 is provided in the example.
- the magnetoresistive element 110 includes the first magnetic layer 11 , the second magnetic layer 12 , and the first nonmagnetic layer 11 N.
- the first magnetic layer 11 is provided between the second conductive layer 12 E and a portion (a third portion 11 Ec described below) of the first conductive layer 11 E.
- the second magnetic layer 12 is provided between the first magnetic layer 11 and the second conductive layer 12 E.
- the first nonmagnetic layer 11 N is provided between the first magnetic layer 11 and the second magnetic layer 12 .
- the first conductive layer 11 E is electrically connected to the first magnetic layer 11 .
- the second conductive layer 12 E is electrically connected to the second magnetic layer 12 .
- the controller 70 is electrically connected to a first portion 11 Ea of the first conductive layer 11 E. For example, the connection is performed by the first interconnect 70 a.
- the controller 70 is electrically connected to a second portion 11 Eb of the first conductive layer 11 E.
- the connection is performed by a third interconnect 70 c.
- the third portion 11 Ec recited above is provided between the first portion 11 Ea and the second portion 11 Eb.
- the controller 70 is electrically connected to the second conductive layer 12 E (the second magnetic layer 12 ).
- the controller 70 implements a first operation and a second operation.
- the controller 70 supplies a first current Ic 1 to the first conductive layer 11 E.
- the first current Ic 1 flows from the first portion 11 Ea toward the second portion 11 Eb.
- the controller 70 supplies a second current Ic 2 to the first conductive layer 11 E.
- the second current Ic 2 flows from the second portion 11 Eb toward the first portion 11 Ea.
- the electrical resistance between the first magnetic layer 11 and the second magnetic layer 12 after the first operation recited above is different from the electrical resistance between the first magnetic layer 11 and the second magnetic layer 12 after the second operation recited above.
- the magnetization of the first magnetic layer 11 after the first operation recited above is in a state corresponding to the orientation of the first current Ic 1 recited above.
- the magnetization of the first magnetic layer 11 after the second operation recited above is in a state corresponding to the orientation of the second current Ic 2 recited above.
- this is based on spin-orbit coupling.
- this is based on spin-Hall effect.
- the angle between the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 after the first operation recited above is different from the angle between the magnetization of the first magnetic layer 11 and the magnetization of the second magnetic layer 12 after the second operation recited above.
- the magnetoresistive element 110 is selected by a voltage applied between the first conductive layer 11 E and the second conductive layer 12 E.
- the magnetization of the first magnetic layer 11 is controlled by the voltage and the orientation of the current recited above.
- a magnetoresistive element and a magnetic memory device can be provided in which the magnetoresistance ratio can be improved.
- perpendicular and parallel refer to not only strictly perpendicular and strictly parallel but also include, for example, the fluctuation due to manufacturing processes, etc. It is sufficient to be substantially perpendicular and substantially parallel.
- magnetoresistive elements and magnetic memory devices practicable by an appropriate design modification by one skilled in the art based on the magnetoresistive elements and the magnetic memory devices described above as embodiments of the invention also are within the scope of the invention to the extent that the spirit of the invention is included.
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Abstract
Description
- This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2016-189475, filed on Sep. 28, 2016; the entire contents of which are incorporated herein by reference.
- Embodiments described herein relate generally to magnetoresistive element and a magnetic memory device.
- There is a magnetoresistive element that uses a MTJ (Magnetic Tunnel Junction) element. The MTJ element uses, for example, the tunneling magnetoresistive (TMR) effect. The magnetoresistive element is, for example, a memory cell of a magnetic memory device such as magnetic random access memory (MRAM), etc. It is desirable for the magnetoresistance ratio of the magnetoresistive element to be high.
-
FIG. 1A andFIG. 1B are schematic cross-sectional views illustrating a magnetoresistive element according to a first embodiment; -
FIG. 2 is a graph illustrating a characteristic of the magnetoresistive element according to the embodiment; -
FIG. 3A toFIG. 3E are photographs illustrating the analysis results of the magnetoresistive element; -
FIG. 4A andFIG. 4B are graphs illustrating analysis results of the magnetoresistive element; -
FIG. 5 is a graph illustrating characteristics of the magnetoresistive element; -
FIG. 6 is a graph illustrating a characteristic of the magnetoresistive element; -
FIG. 7 is a schematic cross-sectional view showing the other magnetoresistive element according to the first embodiment; -
FIG. 8 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 9 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 10 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 11 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 12 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 13 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 14 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 15 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 16 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment; -
FIG. 17 is a schematic cross-sectional view illustrating a magnetic memory device according to a second embodiment; -
FIG. 18A toFIG. 18E are schematic cross-sectional views illustrating the method for manufacturing the magnetic memory device according to the second embodiment; -
FIG. 19 is a schematic view illustrating the magnetic memory device according to the second embodiment; -
FIG. 20 is a schematic view illustrating a magnetic memory device according to the second embodiment; and -
FIG. 21 is a schematic view illustrating another magnetic memory device according to the second embodiment. - According to one embodiment, a magnetoresistive element includes a first magnetic layer, a second magnetic layer, and a first nonmagnetic layer. The first nonmagnetic layer is provided between the first magnetic layer and the second magnetic layer. The first nonmagnetic layer includes an oxide including an inverse-spinel structure.
- According to another embodiment, a magnetoresistive element includes a first magnetic layer, a second magnetic layer, and a first nonmagnetic layer. The first nonmagnetic layer is provided between the first magnetic layer and the second magnetic layer. The first nonmagnetic layer includes an oxide including Ga. The oxide has a plurality of photon energy peaks corresponding to a binding state of the Ga included in the oxide in X-ray absorption near edge structure analysis.
- According to another embodiment, a magnetoresistive element includes a first magnetic layer, a second magnetic layer, and a first nonmagnetic layer. The first nonmagnetic layer is provided between the first magnetic layer and the second magnetic layer. The first nonmagnetic layer includes an oxide. The oxide includes Mg, Ga, and oxygen. The oxide has a first peak intensity of a first photon energy, a second peak intensity of a second photon energy, and an intermediate intensity of a third photon energy in a photon energy range not less than 10370 electron volts and not more than 10385 electron volts in X-ray absorption near edge structure analysis. The second photon energy is larger than the first photon energy. The third photon energy is between the first photon energy and the second photon energy. The intermediate intensity is lower than the first peak intensity and lower than the second peak intensity.
- Various embodiments will be described hereinafter with reference to the accompanying drawings.
- The drawings are schematic and conceptual; and the relationships between the thickness and width of portions, the proportions of sizes among portions, etc., are not necessarily the same as the actual values thereof. Further, the dimensions and proportions may be illustrated differently among drawings, even for identical portions.
- In the specification and drawings, components similar to those described or illustrated in a drawing thereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate.
-
FIG. 1A andFIG. 1B are schematic cross-sectional views illustrating a magnetoresistive element according to a first embodiment. - As shown in
FIG. 1A , themagnetoresistive element 110 according to the embodiment includes a firstmagnetic layer 11, a secondmagnetic layer 12, and a firstnonmagnetic layer 11N. The firstnonmagnetic layer 11N is provided between the firstmagnetic layer 11 and the secondmagnetic layer 12. - The first
magnetic layer 11 is, for example, a ferromagnetic layer. The secondmagnetic layer 12 is, for example, a ferromagnetic layer. The firstnonmagnetic layer 11N is, for example, a tunneling barrier layer. For example, the firstnonmagnetic layer 11N includes an oxide. - In the example of a
magnetoresistive element 110A according to the embodiment as shown inFIG. 1B , abase layer 10S and a secondnonmagnetic layer 12N are provided in addition to the firstmagnetic layer 11, the secondmagnetic layer 12, and the firstnonmagnetic layer 11N. The firstmagnetic layer 11 is provided between thebase layer 10S and the secondmagnetic layer 12. The secondnonmagnetic layer 12N is provided between the firstmagnetic layer 11 and the firstnonmagnetic layer 11N. The secondnonmagnetic layer 12N is, for example, a nonmagnetic metal layer. There are cases where the boundary between the secondnonmagnetic layer 12N and the firstnonmagnetic layer 11N is indistinct. In the case where the secondnonmagnetic layer 12N is thin (e.g., 0.6 nm or less), the secondnonmagnetic layer 12N and the firstnonmagnetic layer 11N may be observed as one layer. - In the embodiment as described below, various layers other than the first
magnetic layer 11, the secondmagnetic layer 12, and the firstnonmagnetic layer 11N may be provided. - For example, the electrical resistance between the first
magnetic layer 11 and the secondmagnetic layer 12 changes when energy (e.g., at least one of a magnetic field, an electric field, a current, a voltage, or stress) is applied to themagnetoresistive elements - For example, the change of the electrical resistance is based on the magnetoresistance effect. For example, the direction of at least one of the magnetization of the first
magnetic layer 11 or the magnetization of the secondmagnetic layer 12 changes according to the applied energy. For example, the angle between these magnetizations changes according to the applied energy. Thereby, the electrical resistance between the firstmagnetic layer 11 and the secondmagnetic layer 12 changes. - For example, the first
magnetic layer 11 functions as, for example, a free layer. The firstmagnetic layer 11 functions as, for example, a memory layer. The secondmagnetic layer 12 functions as, for example, a reference layer. - A first direction that connects the first
magnetic layer 11 and the secondmagnetic layer 12 is taken as a Z-axis direction. One direction perpendicular to the Z-axis direction is taken as an X-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is taken as a Y-axis direction. The first direction corresponds to the stacking direction of the firstmagnetic layer 11, the firstnonmagnetic layer 11N, and the secondmagnetic layer 12. - The first
nonmagnetic layer 11N has a face 11Na crossing the first direction (the Z-axis direction). The face 11Na is, for example, a face opposing the firstmagnetic layer 11. For example, the face 11Na is aligned with the {100} plane. In the embodiment, for example, the face 11Na may not be perfectly parallel to the {100} plane and may be, for example, tilted. The angle between the face 11Na and the {100} plane may be, for example, 10 degrees or less. The {100} plane may be, for example, the plane of the crystal orientation of the firstmagnetic layer 11. - The thickness of the first
nonmagnetic layer 11N (a first nonmagnetic layer thickness t1 referring toFIG. 1A ) is, for example, not less than 0.2 nm (nanometers) and not more than 4 nm. For example, an appropriate tunneling barrier effect is obtained using such a thickness. As described below, a high magnetoresistance ratio is obtained using such a thickness. - The first nonmagnetic layer thickness t1 is the length of the first
nonmagnetic layer 11N along the first direction (the Z-axis direction). The first nonmagnetic layer thickness t1 may be, for example, not less than 1.1 nm and not more than 3.3 nm. The first nonmagnetic layer thickness t1 may be, for example, not less than 1.1 nm and not more than 3.0 nm. The first nonmagnetic layer thickness t1 may be, for example, not less than 1.1 nm and not more than 2.8 nm. - As described above, the first
nonmagnetic layer 11N includes an oxide. The oxide includes, for example, Mg and Ga. The oxide may include MgGa2O4. Other examples of the oxide included in the firstnonmagnetic layer 11N are described below. - In the embodiment, the oxide that is included in the first
nonmagnetic layer 11N includes an inverse-spinel structure. It was found that a high magnetoresistance ratio MR is obtained thereby. For example, a high magnetoresistance ratio MR is obtained while maintaining a low resistance area product RA. The magnetoresistance ratio MR is, for example, the tunneling magnetoresistance ratio (the TMR ratio). - Examples of characteristics of the magnetoresistive element according to the embodiment will now be described. A sample (a first sample) of the experiment described below has the configuration of the
magnetoresistive element 110A. - In the example, the
base layer 10S is a Cr layer. The firstmagnetic layer 11 is an Fe layer. The secondnonmagnetic layer 12N is a Mg layer. The thickness of the Mg layer is 0.6 nm. The firstnonmagnetic layer 11N is a MgGa2O4 layer. The thickness of the MgGa2O4 layer (the first nonmagnetic layer thickness t1) is 3.0 nm. The secondmagnetic layer 12 is an Fe layer. - In the specification, the notation “first material name/second material name” may be used. This notation means that a layer of the first material name is provided on a layer of the second material name. In the specification, the notation “first material name (first length)” may be used. This notation means that the thickness of a layer of the first material name is the first length. For example, the notation “Fe/MgGa2O4 (3.0 nm)” corresponds to the state in which an Fe layer is provided on a layer of MgGa2O4 having a thickness of 3.0 nm.
- A structure of Fe/MgGa2O4 (3.0 nm)/Mg (0.6 nm)/Fe/Cr is provided in the first sample.
- The preparation conditions of the first sample are as follows. A Cr layer is formed by sputtering at room temperature on a substrate (not illustrated); subsequently, heat treatment is performed at 800° C. An Fe layer is formed by sputtering at room temperature on the Cr layer; subsequently, heat treatment is performed at 400 ° C. A Mg layer is formed by sputtering at room temperature on the Fe layer; and a MgGa2O4 layer is formed by sputtering at room temperature on the Mg layer. Subsequently, heat treatment is performed at 500 ° C. An Fe layer is formed by sputtering at room temperature on the MgGa2O4 layer; subsequently, heat treatment is performed at 400 ° C. Thus, the first sample is made.
-
FIG. 2 is a graph illustrating a characteristic of the magnetoresistive element according to the embodiment. - The horizontal axis of
FIG. 2 is an external magnetic field Ha (oersteds (Oe)) applied from the outside to the first sample SP1 (themagnetoresistive element 110A) recited above. The vertical axis is a magnetoresistance ratio MR1 (%). The measurement temperature of the magnetoresistance ratio MR1 is 300 K (Kelvin). - In the first sample SP1 as shown in
FIG. 2 , the magnetoresistance ratio MR1 (at room temperature) is about 121% and is high. For example, this suggests that the coherent tunneling effect arises in the first sample SP1. - An example of structural analysis results of a sample will now be described. The sample of this structural analysis has the structure of the first sample SP1 in which the Mg layer is not provided. In other words, the sample of the structure analysis has the structure of the
magnetoresistive element 110 illustrated inFIG. 1A . Otherwise, the sample of the structure analysis is similar to the first sample SP1. -
FIG. 3A toFIG. 3E are photographs illustrating the analysis results of the magnetoresistive element. -
FIG. 3A is a cross sectional STEM (Scanning Transmission Electron Microscope) image of the sample. The image is observed along the Fe [110] plane.FIG. 3B toFIG. 3D show the analysis results of energy dispersive X-ray spectroscopy (EDS).FIG. 3B toFIG. 3D correspond respectively to the distributions of Mg, Ga, and O.FIG. 3E shows a nano electron diffraction image of the sample. The image is acquired from the region at the vicinity of the firstnonmagnetic layer 11N (the MgGa2O4 layer) inside the sample. The numerals shown inFIG. 3E show the crystal planes of the diffraction spots. - It can be seen from
FIG. 3A that the interface of the MgGa2O4 layer is exceedingly flat. It is considered that the stacked structure inside the sample is formed by epitaxial growth with the (001) orientation. The MgGa2O4 layer has, for example, a cubic inverse-spinel structure. The MgGa2O4 layer may be slightly tetragonally distorted. It is considered that this is due to the effect of the stress generated in the stacked structure including the MgGa2O4 layer. Dislocations substantially are not formed in the MgGa2O4 layer of the sample. A lattice-matched interface is obtained. - As shown in
FIG. 3B toFIG. 3D , the MgGa2O4 layer is uniform. Segregation or elemental interdiffusion at the interfaces is not observed. It can be seen from the RBS analysis results that the MgGa2O4 layer has a substantially stoichiometric composition. - It can be seen from
FIG. 3E that the stacked structure of the sample has the epitaxial relationship of Fe (001) [110]//MgGa2O4 (001) [100]. {022} spots of MgGa2O4 exist inFIG. 3E . Therefore, this suggests that the MgGa2O4 is ordered in a spinel structure. The spinel structure includes a normal spinel structure or an inverse-spinel structure. - As described below, the spinel structure includes an inverse-spinel structure in the sample recited above.
-
FIG. 4A andFIG. 4B are graphs illustrating analysis results of the magnetoresistive element. - These figures show examples of XANES (X-ray absorption near edge structure) analysis results of second to fourth samples SP2 to SP4. The second to fourth samples SP2 to SP4 have configurations similar to that of the first sample SP1 recited above (the structure of the
magnetoresistive element 110A illustrated inFIG. 1B ). The first nonmagnetic layer thickness t1 of the MgGa2O4 layer (the firstnonmagnetic layer 11N) is different between the second to fourth samples SP2 to SP4. The first nonmagnetic layer thickness t1 is 2.8 nm, 1.9 nm, and 1.1 nm respectively in the second to fourth samples SP2 to SP4. The binding state of Ga is focused upon in the analysis results.FIG. 4B is an enlarged view of a portion ofFIG. 4A . In these figures, the horizontal axis is a photon energy Ep (eV). The vertical axis is an intensity Int. The intensity Int is displayed as being normalized. In the second to fourth samples SP2 to SP4, heat treatment at 400 ° C. is performed after forming the Mg layer and the MgGa2O4 layer by sputtering at room temperature. Other than the different temperatures, the second to fourth samples SP2 to SP4 are made using conditions similar to those of the first sample SP1. - In
FIG. 4A andFIG. 4B , peaks are obtained in a range of the photon energy Ep not less than 10370 eV (electron volts) and not more than 10385 eV. The peaks are related to the binding state of Ga. In the example, the peaks correspond to the peaks of the photon energy Ep corresponding to the electron energy of the Ga—K shell. - In the case where the first nonmagnetic layer thickness t1 is 1.1 nm, two peaks are observed distinctly in the range of the photon energy Ep. One of the two peaks (the peak on the low-energy side) corresponds to the peak when the Ga exists in a tetrahedral configuration (a first state). The other one of the two peaks (the peak on the high-energy-side) corresponds to the peak when the Ga exists in an octahedral configuration (a second state).
- The two peaks are observed for the fourth sample SP4 in which the first nonmagnetic layer thickness t1 is 1.1 nm. It is estimated that the first state and the second state recited above exist in the fourth sample SP4. A valley is observed between the two peaks. The intensity Int at the valley is lower than the intensities Int at the two peaks. In the fourth sample SP4, the intensities Int of the two peaks are substantially the same.
- In a perfect inverse-spinel structure, the amount (the density) of Ga at the tetrahedral sites and the amount (the density) of Ga at the octahedral sites are the same. Therefore, in the sample in which the first nonmagnetic layer thickness t1 is 1.1 nm, it is estimated that a substantially perfect inverse-spinel structure is provided.
- Two peaks are observed also for the third sample SP3 in which the first nonmagnetic layer thickness t1 is 1.9 nm. In the third sample, the intensity Int of the peak on the low-energy side is lower than the intensity Int of the peak on the high-energy-side. In the third sample SP3, it is considered that the region of the first state is relatively small. In the third sample SP3, a valley is observed between the two peaks.
- On the other hand, in the second sample SP2 in which the first nonmagnetic layer thickness t1 is 2.8 nm, the peak on the low-energy side has a shoulder-like shape.
- The intensity Int of the peak on the low-energy side relatively increases as the first nonmagnetic layer thickness t1 decreases. This suggests an increase of the spinel inversion degree.
- In the case where at least two peaks are observed, it is clear that the inverse-spinel structure exists. In the case where the peak on the low-energy side has a shoulder-like shape as well, the shoulder originates in the inverse-spinel structure. The inverse-spinel structure is included for the shoulder-like shape as well.
- In the embodiment, for example, the oxide included in the first
nonmagnetic layer 11N includes Ga; and the oxide has multiple photon energy peaks corresponding to the binding state of the Ga included in the oxide in X-ray absorption near edge structure analysis. For example, in the X-ray absorption near edge structure analysis, the oxide has multiple photon energy peaks corresponding to the electron energy of the Ga—K shell included in the oxide. - In the embodiment, for example, in the case where the oxide included in the first
nonmagnetic layer 11N includes Mg, Ga, and oxygen, the oxide has two peak intensities and an intermediate intensity (a valley) between the two peaks in the range of the photon energy Ep of not less than 10370 eV and not more than 10385 eV in XANES analysis. One of the two peak intensities is a first peak intensity of a first photon energy (in the example, not less than 10373 eV and but than 17376 eV). The other one of the two peak intensities is a second peak intensity of a second photon energy (in the example, greater than 10376 eV and not more than 10385 eV). The second photon energy is larger than the first photon energy. The intermediate intensity is an intensity corresponding to a third photon energy. The third photon energy is between the first photon energy and the second photon energy. The intermediate intensity of the third photon energy is lower than the first peak intensity and lower than the second peak intensity. The firstnonmagnetic layer 11N includes the inverse-spinel structure if at least such an intermediate intensity (valley) is observed. - The first
nonmagnetic layer 11N (the MgGa2O4 layer) includes the inverse-spinel structure in the sample illustrated inFIG. 3A toFIG. 3E as well. The shoulder recited above is observed. - In the samples recited above, heat treatment is performed after the film deposition of each layer. The state of the crystal of the first
nonmagnetic layer 11N changes according to the conditions of the heat treatment. For example, the state of the crystal changes according to the temperature, time, etc., of the heat treatment. The state of the crystal changes also according to the rising curve, the cooling curve, etc., of the temperature of the heat treatment. The oxide that includes the inverse-spinel structure is obtained by employing the appropriate preparation conditions. - For example, a thin oxide layer (the first
nonmagnetic layer 11N) that is 4 nm or less is affected easily by the layers adjacent to the oxide layer. For example, the thin oxide layer is affected easily by the firstmagnetic layer 11 or the secondmagnetic layer 12. For example, the thin oxide layer is affected easily by the secondnonmagnetic layer 12N or thebase layer 10S used as the foundation. By employing appropriate preparation conditions, the inverse-spinel structure can be formed in the thin oxide layer as well. - It is considered that the structure (the proportion of normal spinel, inverse spinel, and amorphous) of the layer of MgGa2O4 changes according to the preparation conditions, the thickness, etc. The inverse-spinel structure is obtained by using the appropriate preparation conditions and thickness. For example, the state of the crystal also changes according to the temperature of the heat treatment, the time of the processing, the temperature change curve (rising and cooling), etc. For example, the crystallinity relates also to the oxygen concentration range in the oxygen charging during the heat treatment or after the heat treatment. For example, the crystallinity is affected by whether the heat treatment is performed after the formation of each of the multiple layers or whether the heat treatment is performed collectively after the formation of the multiple layers. The change of the crystallinity also includes, for example, a portion of Ga3+ being reduced easily in the metal Ga. If the film deposition rate is high, the crystallinity and the flatness improve; and the inverse-spinel structure is obtained easily. For example, if the thickness is thin, the proportion of the inverse-spinel structure increases. When excessively thin, the film thickness is not more than the critical film thickness of crystallization; and the amorphous proportion increases. The thickness of the layer of MgGa2O4 (the first
nonmagnetic layer 11N) is, for example, not less than 1.1 nm and not more than 3.3 nm. - Generally, a spinel-structure oxide is notated (A1-xBx)[AxB2-x]O4. In the notation, “x” is the spinel inversion degree. “A” and “B” are main group elements or elements of transition metals. “A” is, for example, an element that forms a divalent cation. “B” is an element that forms a trivalent cation. “O” is oxygen. In the notation, the elements inside the “( )”brackets are arranged to occupy ⅛ of the tetrahedral interstices of the cubic lattice formed of the oxygen ions. For example, the arrangement of the elements inside the “( )”brackets is ordered. In the notation, the elements inside the “[ ]” brackets are arranged to occupy ½ of the octahedral interstices. For example, the arrangement of the elements inside the “[ ]” brackets is ordered. The former and the latter each form spinel structures.
- For example, x=0 in a normal spinel structure. The normal spinel structure is notated as (A)[B2]O4. On the other hand, in an inverse-spinel structure, x=1. The inverse-spinel structure is notated as (B)[AB]O4.
- Typical element metals that are included in the spinel structure include, for example, an element forming a divalent cation and an element forming a trivalent cation. The element that forms the divalent cation includes, for example, at least one selected from the group consisting of Zn and Mg. The element that forms the trivalent cation includes, for example, at least one selected from the group consisting of In, Ga, and Al.
- The ease of oxygen entering the tetrahedral sites is, for example, (easy) Zn>In>Ga>Mg>Al (difficult). For example, In or Ga occupy the tetrahedral sites more easily than does Mg. For example, MgGa2O4 and MgIn2O4 include inverse-spinel structures as stable structures.
- For example, there is a reference example in which rock-salt MgO is used as a tunneling barrier layer (e.g., the first
nonmagnetic layer 11N). A high magnetoresistance ratio MR (e.g., about 300%) is obtained in the reference example. However, the bandgap of MgO is 7 eV to 8 eV and is high; therefore, the resistance area product is high. In a magnetic memory device that uses a magnetoresistive element, the resistance becomes high when the storage density is increased and the element size is reduced. Therefore, for the configuration of the reference example, the thickness of the MgO layer is set to be extremely thin when reducing the element size. However, for the thin MgO, the insulative properties degrade; and the manufacturing yield or the reliability decreases. - Conversely, in the oxide according to the embodiment as described below, a low resistance area product is obtained. It is considered that this is caused by the small bandgap of the oxide according to the embodiment. As described below, for example, the bandgap of MgGa2O4 is about 4.7 eV (not less than 4.7 eV and not more than 4.9 eV).
- According to the embodiment, a high magnetoresistance ratio MR can be obtained while maintaining a low resistance area product.
- It is considered that the high magnetoresistance ratio MR obtained for a rock-salt MgO case originates in the crystal structure of the rock-salt MgO. In rock-salt MgO, the Mg is arranged at all of the octahedral sites of oxygen.
- On the other hand, in MgGa2O4 (i.e., (Ga)[MgGa]O4), considering the two types of spinel structures, the inverse-spinel structure is closer to the structure of MgO than is the normal spinel structure. It is considered that the high magnetoresistance ratio MR obtained for MgGa2O4 having the inverse-spinel structure relates to the inverse-spinel structure being closer to the structure of MgO. Thus, it is considered that the high MR ratio obtained using the oxide (MgGa2O4, MgIn2O4, etc.) of the first
nonmagnetic layer 11N is based on the inverse-spinel structure. - As described below, a low resistance area product RA is obtained for MgGa2O4 and the like.
- On the other hand, MgAl2O4 has a normal spinel structure as a ground state. According to experiments of the inventors of the application, it was found that cation sites are ordered self-organizingly in MgGa2O4 similarly to MgO even by a room-temperature film deposition process. Therefore, the inverse-spinel structure is formed more easily in MgGa2O4 than in MgAl2O4.
- Due to the property of being ordered self-organizingly, for example, a wider selection is possible for the layers (e.g., the first
magnetic layer 11, etc.) other than the firstnonmagnetic layer 11N. For example, the firstnonmagnetic layer 11N may be a monocrystal or may be a polycrystal. In the case where the firstnonmagnetic layer 11N includes a polycrystal, for example, an oriented film is included in the firstnonmagnetic layer 11N. - In the embodiment, the oxide included in the first
nonmagnetic layer 11N is, for example, Mg1-xGaxOy (x being greater than 0 and less than 1, and y being not less than 3 and not more than 5). Or, the oxide included in the firstnonmagnetic layer 11N is, for example, Mg1-xInxOy (x being greater than 0 and less than 1, and y being not less than 3 and not more than 5). For example, an inverse-spinel structure is obtained for such composition ranges. Other examples of the oxide are described below. - Examples of analysis methods of the crystalline state of the first
nonmagnetic layer 11N of will now be described. - For example, information that relates to the crystalline state of the first
nonmagnetic layer 11N is obtained by a structure analysis method using a TEM (Transmission Electron Microscope). For example, by TEM, information that relates to the crystal pattern, the existence of lattice defects, the direction of the crystal orientation, etc., is obtained. For example, information that relates to the organization structure and the crystal structure in an atomic scale can be obtained by also acquiring the electron diffraction pattern. For example, information that relates to whether or not the structure is an inverse-spinel structure is obtained by focusing on designated diffraction spots. - For example, the information that relates to the crystalline state of the first
nonmagnetic layer 11N is obtained by HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy TEM). In this analysis method, electrons that are irradiated on the atoms and scattered are detected. Contrast that is proportional to an atomic number is obtained. Information that relates to the atomic arrangement is obtained by focusing on the contrast. The information that relates to whether or not the structure is an inverse-spinel structure is obtained. - For example, the information that relates to the crystalline state of the first
nonmagnetic layer 11N is obtained by XAFS (X-ray absorption fine structure) analysis, EXAFS (Extended X-ray Absorption Fine Structure) analysis, XANES analysis, etc. In these analysis methods, structure analysis and analysis relating to the chemical states are possible. In these methods, non-destructive structure analysis or chemical state analysis in the depth direction is possible by selecting the analysis depth (surface or bulk). In XANES analysis, information that relates to the coordination structure of the elemental components is obtained. The information that relates to whether or not the structure is an inverse-spinel structure is obtained. - In a magnetic memory device that uses a magnetoresistive element, the resistance value increases when downscaling is performed. Therefore, it is desirable to reduce the resistance area product RA of the magnetoresistive element. There are reference examples in which MgO or MgAl2O4 is used as the barrier layer (e.g., the first
nonmagnetic layer 11N). In these reference examples, the decrease of the resistance area product RA as a material is limited; and it is necessary to reduce the thickness of the barrier layer. In the case where the thickness of the barrier layer is reduced, the breakdown voltage of the barrier layer degrades abruptly. Therefore, the improvement of the magnetoresistance ratio MR ratio and the reduction of the resistance area product RA are desirable. - An example of the resistance area product RA of the magnetoresistive element according to the embodiment will now be described.
-
FIG. 5 is a graph illustrating characteristics of the magnetoresistive element. -
FIG. 5 shows an example of the resistance area product RA for samples (including, for example, the first to fourth samples SP1 to SP4, etc.) in which the firstnonmagnetic layer 11N is MgGa2O4, and samples (the reference example) in which the firstnonmagnetic layer 11N is MgAl2O4. In these samples, the firstmagnetic layer 11 and the secondmagnetic layer 12 both are Fe layers. The horizontal axis ofFIG. 5 is the first nonmagnetic layer thickness t1 (nm). The vertical axis is the resistance area product RA (Ω·μm2). The resistance area product RA corresponds to the state in which the magnetization of the firstmagnetic layer 11 and the magnetization of the secondmagnetic layer 12 are in a parallel state. The measurement temperature is 300 K. In the sample of MgGa2O4, the MgGa2O4 includes an inverse-spinel structure. In the sample of MgAl2O4 (the reference example), the MgAl2O4 includes a normal spinel structure. - As shown in
FIG. 5 , for the same first nonmagnetic layer thickness t1, the resistance area product RA of MgGa2O4 is lower than the resistance area product RA of MgAl2O4. Such a characteristic is confirmed at least for the case where the first nonmagnetic layer thickness t1 is not less than 1.1 nm and not more than 3.3 nm. - Thus, a low resistance area product RA is obtained using the MgGa2O4 (the first
nonmagnetic layer 11N) according to the embodiment. According to the embodiment, a low resistance area product RA is obtained while obtaining a high magnetoresistance ratio MR. For example, the firstnonmagnetic layer 11N is not excessively thin. Thereby, high reliability is obtained. According to the embodiment, a high magnetoresistance ratio MR is obtained. Further, a low resistance area product RA is obtained. High reliability is obtained - For the two samples as shown in
FIG. 5 , the logarithm of the resistance area product RA increases linearly with the first nonmagnetic layer thickness t1. This suggests that the direct tunneling mode is dominant in these samples. - The change rate (the slope) of the increase of the resistance area product RA for the increase of the thickness in the sample of MgGa2O4 is lower than that of the sample of MgAl2O4. Therefore, this suggests that the barrier height of the sample of MgGa2O4 is lower than the barrier height of the sample of MgAl2O4.
-
FIG. 6 is a graph illustrating a characteristic of the magnetoresistive element. -
FIG. 6 shows examples of the current density of the two samples shown inFIG. 5 . The horizontal axis ofFIG. 6 is a bias voltage Vb (volts (V)). The vertical axis is a current density CD (A/cm2). The measurement temperature is 300 K. InFIG. 6 , the solid lines correspond to the state in which the magnetization of the firstmagnetic layer 11 and the magnetization of the secondmagnetic layer 12 are parallel. The dotted lines correspond to the state in which the magnetization of the firstmagnetic layer 11 and the magnetization of the secondmagnetic layer 12 are antiparallel. - In the sample of MgGa2O4 as shown in
FIG. 6 , the bias voltage Vb at which the current density CD changes abruptly is about 0.6 V. Conversely, in the sample of MgAl2O4, the bias voltage Vb at which the current density CD changes abruptly is about 1.1 V. - Generally, the bias voltage Vb at which the current density CD increases abruptly is related to the barrier height. From the results of
FIG. 6 , this suggests that the barrier height of MgGa2O4 is lower than the barrier height of MgAl2O4. - There is a correlation between the bandgap and the barrier height. The barrier height is reduced by reducing the bandgap. For example, by reducing the bandgap, for example, the resistance area product RA is reduced.
- A high magnetoresistance ratio (MR ratio) is obtained for MgO or MgAl2O4. The bandgaps of these materials are 7 eV to 8 eV.
- According to REELS (reflection electron energy loss spectroscopy) analysis results, the bandgap of MgGa2O4 is estimated to be about 4.7 eV. Thus, the bandgap of MgGa2O4 is smaller than the bandgap of MgO or MgAl2O4. For example, the barrier height of MgGa2O4 is lower than the barrier height of MgO or MgAl2O4. For the same first nonmagnetic layer thickness t1, the resistance area product RA of MgGa2O4 is lower than the resistance area product RA of MgO or MgAl2O4.
- In the embodiment, it is favorable for the bandgap of the oxide included in the first
nonmagnetic layer 11N to be, for example, less than 7 eV. It is more favorable for the bandgap of the oxide to be 5 eV or less. - On the other hand, when the bandgap is excessively small, for example, there are cases where it is difficult to maintain the tunneling transport mode and, for example, the MR ratio cannot be sufficiently high. In the embodiment, it is favorable for the bandgap of the oxide included in the first
nonmagnetic layer 11N to be 2 eV or more; and it is more favorable to be 3 eV or more. - In the embodiment, it is favorable for the difference between the in-plane lattice constant of the first
nonmagnetic layer 11N and the in-plane lattice constant of the firstmagnetic layer 11 to be small, and for the difference between the in-plane lattice constant of the firstnonmagnetic layer 11N and the in-plane lattice constant of the secondmagnetic layer 12 to be small. For example, an interface that has substantially no dislocations is obtained. For example, the wave number selectivity of the tunneling electrons is not obstructed. For example, a high magnetoresistance ratio MR is obtained. - The magnetic layers that are included in the magnetoresistive element include, for example, a cubic material having a lattice constant that is about the same as that of Fe. Or, the magnetic layers include a tetragonal material having a lattice constant that is about the same as that of MnGa.
- In the embodiment, for example, it is favorable for the oxide included in the first
nonmagnetic layer 11N to include a material having good lattice matching with both Fe and MnGa. The a-axis lattice constant of Fe is 0.287 nm. The lattice constant is 0.405 nm when rotated 45 degrees in the plane. On the other hand, the a-axis lattice constant of MnGa is 0.389 nm. - For example, it is favorable for ½ of the lattice constant of the first
nonmagnetic layer 11N to be not less than 0.3775 nm and not more than 0.4255 nm. The lower limit and the upper limit correspond respectively to 0.755 nm/2 and 0.851 nm/2. Thereby, the firstnonmagnetic layer 11N matches the cubic magnetic layer of Fe and the like with a lattice constant difference within 5%. - Or, for example, it is favorable for ½ of the lattice constant of the first
nonmagnetic layer 11N to be not less than 0.370 nm and not more than 0.409 nm. The lower limit and the upper limit correspond respectively to 0.740 nm/2 and 0.818 nm/2. Thereby, the firstnonmagnetic layer 11N matches the tetragonal magnetic layer of MnGa and the like with a lattice constant difference within 5%. - For example, the lattice constants recited above correspond to the lattice constants in one direction in the X-Y plane.
- In the
magnetoresistive element 110A described in reference toFIG. 1B , for example, the oxidation state of the interface is well-controlled by the Mg layer (the secondnonmagnetic layer 12N). In the embodiment, the secondnonmagnetic layer 12N may be omitted. - In the magnetoresistive elements (e.g., the
magnetoresistive element 110, etc.) according to the embodiment, the oxide included in the firstnonmagnetic layer 11N is, for example, crystalline with the {100} plane and includes divalent cations and trivalent cations. The oxide has the inverse-spinel structure as a stable structure. - In the embodiment, for example, the electrical resistance of the magnetoresistive element changes due to energy supplied from the outside such as a write current, etc. For example, the change of the electrical resistance is based on the difference of the angles between the magnetization of the first
magnetic layer 11 and the magnetization of the secondmagnetic layer 12. An example of the energy supplied from the outside is the write current. For example, the write current flows to the Z-axis direction. - For example, the direction of the magnetization of one of the first
magnetic layer 11 or the secondmagnetic layer 12 substantially does not change before and after the supply of the write current to the magnetoresistive element. The direction of the other magnetization of the firstmagnetic layer 11 or the secondmagnetic layer 12 changes before and after the supply of the write current. For example, the former corresponds to the reference layer. The latter corresponds to a memory layer (or a free layer). - For example, an example of the change of the magnetization in the case where the first
magnetic layer 11 is a memory layer and the secondmagnetic layer 12 is a reference layer will now be described. - For example, the write current is supplied in the direction from the first
magnetic layer 11 toward the secondmagnetic layer 12 in the case where the magnetization of the firstmagnetic layer 11 and the magnetization of the secondmagnetic layer 12 are antiparallel to each other. Electrons pass through the firstnonmagnetic layer 11N from the secondmagnetic layer 12 and flow in the firstmagnetic layer 11. The electrons are spin-polarized by passing through the secondmagnetic layer 12. The spin-polarized electrons flow in the firstmagnetic layer 11. The spin-polarized electrons that have the spin in the same direction as the magnetization of the firstmagnetic layer 11 pass through the firstmagnetic layer 11. On the other hand, the spin-polarized electrons that have the spin in the opposite direction of the magnetization of the firstmagnetic layer 11 apply spin-torque to the magnetization of the firstmagnetic layer 11. The direction of the magnetization of the firstmagnetic layer 11 changes to the same orientation as the magnetization of the secondmagnetic layer 12. The direction of the magnetization of the firstmagnetic layer 11 reverses. The magnetization of the firstmagnetic layer 11 becomes parallel to (the same direction as) the direction of the magnetization of the secondmagnetic layer 12. - On the other hand, in the case where the direction of the magnetization of the first
magnetic layer 11 and the direction of the magnetization of the secondmagnetic layer 12 are parallel to each other, the write current is supplied from the secondmagnetic layer 12 toward the firstmagnetic layer 11. The electrons pass through the firstnonmagnetic layer 11N from the firstmagnetic layer 11 and flow in the secondmagnetic layer 12. The electrons are spin-polarized by passing through the firstmagnetic layer 11. The spin-polarized electrons flow in the secondmagnetic layer 12. The spin-polarized electrons that have the spin in the same direction as the magnetization of the secondmagnetic layer 12 pass through the secondmagnetic layer 12. On the other hand, the spin-polarized electrons that have the spin of the opposite orientation of the magnetization of the secondmagnetic layer 12 are reflected by the interface between the firstnonmagnetic layer 11N and the secondmagnetic layer 12, pass through the firstnonmagnetic layer 11N, and flow into the secondmagnetic layer 12. These electrons apply spin-torque to the magnetization of the firstmagnetic layer 11 and act to cause the direction of the magnetization of the firstmagnetic layer 11 to be oriented in the opposite direction of the magnetization of the secondmagnetic layer 12. The direction of the magnetization of the firstmagnetic layer 11 reverses. The magnetization of the firstmagnetic layer 11 becomes antiparallel to the direction of the magnetization of the secondmagnetic layer 12. - In the embodiment, the first
magnetic layer 11 and the secondmagnetic layer 12 are mutually interchangeable. For example, the firstmagnetic layer 11 may be the reference layer; and the secondmagnetic layer 12 may be the memory layer. - In the embodiment, it is favorable for at least one of the coercivity, an anisotropic magnetic field Hk, or a Gilbert damping constant α to be different between the first
magnetic layer 11 and the secondmagnetic layer 12; and, for example, the angle of the magnetization direction can be controlled more stably. - For example, the magnetic layer in which one of the coercivity, the anisotropic magnetic field Hk, or the Gilbert damping constant α is relatively large corresponds to the reference layer. The magnetic layer in which one of the coercivity, the anisotropic magnetic field Hk, or the Gilbert damping constant α is relatively small corresponds to the memory layer.
- Several examples of another magnetoresistive element according to the embodiment will now be described. The magnetoresistive element recited below also includes the first
magnetic layer 11, the secondmagnetic layer 12, and the firstnonmagnetic layer 11N. Thebase layer 10S (e.g., a metal layer of Cr, etc.) may be further provided. The magnetoresistive element is similar to themagnetoresistive element nonmagnetic layer 12N may be provided in the several examples of the magnetoresistive element described below. - In the following description, the notation “first element name (second element name)” means the state in which the element of the second element name is included in the material of the first element name or the state in which the second element substantially is not included. For example, the notation “CoFe(B)” corresponds to the state in which CoFe is included or the state in which CoFeB is included.
- In the following description, the notation “material name (plane orientation)” means that one surface (a film surface) of a layer of the material name is aligned with the plane orientation. For example, the notation “MnGa (001)” corresponds to the state in which a layer of MnGa is stacked with another layer, and one surface of the MnGa is aligned with the (001) plane. The one surface crosses a direction (the stacking direction) connecting the layer of MnGa and the other layer. The one surface is, for example, a surface aligned with the X-Y plane.
FIG. 7 is a schematic cross-sectional view showing the other magnetoresistive element according to the first embodiment. - As shown in
FIG. 7 , a thirdmagnetic layer 13 is provided in the othermagnetoresistive element 111 according to the embodiment. The thirdmagnetic layer 13 is provided between the firstmagnetic layer 11 and the firstnonmagnetic layer 11N. - For example, the state in which the first
magnetic layer 11 and the thirdmagnetic layer 13 are magnetically coupled to each other is favorable. For example, the magnetization of the firstmagnetic layer 11 reverses as one body with the thirdmagnetic layer 13. For example, the magnetization of the thirdmagnetic layer 13 reverses as one body with the firstmagnetic layer 11. The orientation of the magnetization of the firstmagnetic layer 11 is substantially the same as the orientation of the magnetization of the thirdmagnetic layer 13. - For example, the spin polarization can be large by using the third
magnetic layer 13. Thereby, the magnetoresistance ratio MR can be increased further. - In a first example of the
magnetoresistive element 111, the firstmagnetic layer 11 includes MnGa. The thirdmagnetic layer 13 includes CoFe(B). The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa2O4 (001)/CoFe(B) (001)/MnGa (001) is obtained. - In a second example of the
magnetoresistive element 111, the firstmagnetic layer 11 includes MnGa. The thirdmagnetic layer 13 includes Co2FeAl. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa2O4 (001)/Co2FeAl (001)/MnGa (001) is obtained. - In a third example of the
magnetoresistive element 111, the firstmagnetic layer 11 includes MnGa. The thirdmagnetic layer 13 includes Fe3O4. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa2O4 (001)/Fe3O4 (001)/MnGa (001) is obtained. -
FIG. 8 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 8 , themagnetoresistive element 111A according to the embodiment includes the thirdmagnetic layer 13 and a firstintermediate layer 21. The thirdmagnetic layer 13 is provided between the firstmagnetic layer 11 and the firstnonmagnetic layer 11N. The firstintermediate layer 21 is provided between the firstmagnetic layer 11 and the thirdmagnetic layer 13. - For example, the spin polarization is increased by the third
magnetic layer 13. For example, the crystal structure between the firstmagnetic layer 11 and the thirdmagnetic layer 13 is adjusted by the firstintermediate layer 21. For example, the diffusion of the elements is suppressed by the firstintermediate layer 21. - In a first example of the
magnetoresistive element 111A, the firstmagnetic layer 11 includes MnGa. The firstintermediate layer 21 includes an amorphous layer. The thirdmagnetic layer 13 includes, for example, CoFe(B). The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa2O4 (001)/CoFe(B) (001)/amorphous layer/MnGa (001) is provided. - For example, at least a portion of the third
magnetic layer 13 becomes amorphous during the film deposition due to the amorphous firstintermediate layer 21. For example, the orientation of the firstnonmagnetic layer 11N improves. The amorphous layer of the firstintermediate layer 21 includes, for example, at least one element selected from the group consisting of Mg, Ba, Ca, Sr, Sc, Y, Ta, W, Nb, Gd, Tb, Dy, Ce, Ho, Yb, Er, B, C, and N. - In a second example of the
magnetoresistive element 111A, the firstmagnetic layer 11 includes MnGa. The firstintermediate layer 21 includes a crystalline layer. The thirdmagnetic layer 13 includes Co2FeAl. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa2O4 (001)/Co2FeAl (001)/crystalline layer/MnGa (001) is provided. -
FIG. 9 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 9 , themagnetoresistive element 111B according to the embodiment includes a fourthmagnetic layer 14. The fourthmagnetic layer 14 is provided between the secondmagnetic layer 12 and the firstnonmagnetic layer 11N. - The fourth
magnetic layer 14 is magnetically coupled to, for example, the secondmagnetic layer 12. For example, the spin polarization is increased by providing the fourthmagnetic layer 14. - In a first example of the
magnetoresistive element 111B, for example, the firstmagnetic layer 11 includes CoFe(B). The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes CoFe(B). The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/CoFe(B) (001)/MgGa2O4 (001)/CoFe(B) (001) is provided. - In a second example of the
magnetoresistive element 111B, the firstmagnetic layer 11 includes Co2FeAl. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes Co2FeAl. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/Co2FeAl (001)/MgGa2O4 (001)/Co2FeAl (001) is provided. -
FIG. 10 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 10 , themagnetoresistive element 111C according to the embodiment includes the fourthmagnetic layer 14 and a secondintermediate layer 22. The fourthmagnetic layer 14 is provided between the secondmagnetic layer 12 and the firstnonmagnetic layer 11N. The secondintermediate layer 22 is provided between the fourthmagnetic layer 14 and the secondmagnetic layer 12. - The fourth
magnetic layer 14 is magnetically coupled to, for example, the secondmagnetic layer 12. For example, the spin polarization is increased by providing the fourthmagnetic layer 14. - For example, the crystal structure between the second
magnetic layer 12 and the fourthmagnetic layer 14 is adjusted by the secondintermediate layer 22. For example, the diffusion of the elements is suppressed by the secondintermediate layer 22. - In a first example of the
magnetoresistive element 111C, the firstmagnetic layer 11 includes CoFe(B). The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes CoFe(B). The secondintermediate layer 22 includes an amorphous layer. The secondmagnetic layer 12 includes CoPt. For example, the orientation relationship of CoPt (111)/amorphous layer/CoFe(B) (001)/MgGa2O4 (001)/CoFe(B) (001) is provided. By using the amorphous layer, the difference of the crystal types between the secondmagnetic layer 12 and the fourthmagnetic layer 14 is reset. The amorphous layer that is used to form the secondintermediate layer 22 includes, for example, at least one element selected from the group consisting of Ta, W, Mo, Nb, Ru, Rh, and Ir. - In a second example of the
magnetoresistive element 111C, the firstmagnetic layer 11 includes Co2FeAl. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes Co2FeAl. The secondintermediate layer 22 includes a crystalline layer. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/crystalline layer/Co2FeAl (001)/MgGa2O4 (001)/Co2FeAl (001) is provided. -
FIG. 11 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 11 , themagnetoresistive element 111D according to the embodiment includes the thirdmagnetic layer 13 and the fourthmagnetic layer 14. - In a first example of the
magnetoresistive element 111D, the firstmagnetic layer 11 includes MnGa. The thirdmagnetic layer 13 includes CoFe(B). The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes CoFe(B). The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/CoFe(B) (001)/MgGa2O4 (001)/CoFe(B) (001)/MnGa (001) is provided. - In a second example of the
magnetoresistive element 111D, the firstmagnetic layer 11 includes MnGa. The thirdmagnetic layer 13 includes Co2FeAl. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes Co2FeAl. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/Co2FeAl (001)/MgGa2O4 (001)/Co2FeAl (001)/MnGa (001) is provided. -
FIG. 12 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 12 , themagnetoresistive element 111E according to the embodiment includes the firstintermediate layer 21, the thirdmagnetic layer 13, the fourthmagnetic layer 14, and the secondintermediate layer 22. - In a first example of the
magnetoresistive element 111E, the firstmagnetic layer 11 includes MnGa. The firstintermediate layer 21 includes an amorphous layer. The thirdmagnetic layer 13 includes CoFe(B). The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes CoFe(B). The secondintermediate layer 22 includes an amorphous layer. The secondmagnetic layer 12 includes CoPt. For example, the orientation relationship of CoPt (111)/amorphous layer/CoFe(B) (001)/MgGa2O4 (001)/CoFe(B) (001)/amorphous layer/MnGa (001) is provided. In a second example of themagnetoresistive element 111E, the firstmagnetic layer 11 includes MnGa. The firstintermediate layer 21 includes a crystalline layer. The thirdmagnetic layer 13 includes Co2FeAl. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourthmagnetic layer 14 includes Co2FeAl. The secondintermediate layer 22 includes a crystalline layer. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/crystalline layer/Co2FeAl (001)/MgGa2O4 (001)/Co2FeAl (001)/crystalline layer/MnGa (001) is provided. - In a third example of the
magnetoresistive element 111E, the firstmagnetic layer 11 includes MnGa. The firstintermediate layer 21 includes a crystalline layer. The thirdmagnetic layer 13 includes Fe3O4. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The fourth magnetic layer includes Co2FeAl. The secondintermediate layer 22 includes a crystalline layer. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/crystalline layer/Co2FeAl (001)/MgGa2O4 (001)/Fe3O4 (001)/crystalline layer/MnGa (001) is provided. -
FIG. 13 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 13 , themagnetoresistive element 111F according to the embodiment includes the firstmagnetic layer 11, the firstnonmagnetic layer 11N, and the secondmagnetic layer 12. - In a first example of the
magnetoresistive element 111F, the firstmagnetic layer 11 includes CoFe(B). The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The secondmagnetic layer 12 includes CoFe(B). The orientation relationship of CoFe(B) (001)/MgGa2O4 (001)/CoFe(B) is provided. - In a second example of the
magnetoresistive element 111F, the firstmagnetic layer 11 includes MnGa. The firstnonmagnetic layer 11N includes crystalline MgGa2O4. The secondmagnetic layer 12 includes MnGe. For example, the orientation relationship of MnGe (001)/MgGa2O4 (001)/MnGa (001) is provided. -
FIG. 14 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 14 , themagnetoresistive element 111G according to the embodiment includes the thirdmagnetic layer 13, the fourthmagnetic layer 14, a thirdnonmagnetic layer 13N, and a fifthmagnetic layer 15. - The second
magnetic layer 12 is provided between the firstmagnetic layer 11 and the fifthmagnetic layer 15. The thirdnonmagnetic layer 13N is provided between the secondmagnetic layer 12 and the fifthmagnetic layer 15. In such a case as well, the thirdmagnetic layer 13 also is provided between the firstmagnetic layer 11 and the firstnonmagnetic layer 11N. The fourthmagnetic layer 14 is provided between the secondmagnetic layer 12 and the firstnonmagnetic layer 11N. - In the example, the fourth
magnetic layer 14 and the secondmagnetic layer 12 are reference layers. The thirdmagnetic layer 13 and the firstmagnetic layer 11 are memory layers. - The fifth
magnetic layer 15 functions as, for example, a bias layer or a shift adjustment layer. The magnetization of the fifthmagnetic layer 15 is antiparallel to (the opposite orientation of) the orientation of the magnetization of the secondmagnetic layer 12. The fifthmagnetic layer 15 may have antiferromagnetic (synthetic anti-ferromagnetic) coupling to the secondmagnetic layer 12 via the thirdnonmagnetic layer 13N. Thereby, for example, the shift of the current of the magnetization reversal of the memory layer due to the stray magnetic field from the reference layer can be suppressed. For example, the shift of the current of the magnetization reversal due to the stray magnetic field can be adjusted. - It is favorable for the third
nonmagnetic layer 13N to have high heat resistance. For example, thermal mixing between the secondmagnetic layer 12 and the fifthmagnetic layer 15 due to the annealing processes can be suppressed. For example, it is favorable for the thirdnonmagnetic layer 13N to have the function of controlling the orientation of the crystal when forming the fifthmagnetic layer 15. - In the case where the third
nonmagnetic layer 13N is excessively thick, the distance between the fifthmagnetic layer 15 and the memory layer (in the example, the firstmagnetic layer 11, etc.) is longer. Therefore, there are cases where the shift adjustment magnetic field applied to the memory layer from the fifthmagnetic layer 15 decreases. It is favorable for the thickness of the thirdnonmagnetic layer 13N to be, for example, 5 nm or less. Thereby, the decrease of the shift adjustment magnetic field recited above is suppressed. - The fifth
magnetic layer 15 includes, for example, a ferromagnetic material having an easy magnetization axis in a direction perpendicular to the film face. For example, the distance between the fifthmagnetic layer 15 and the memory layer is longer than the distance between the reference layer and the memory layer. For example, it is favorable for the thickness of the fifthmagnetic layer 15 to be thicker than the thickness of the reference layer. For example, the saturation magnetization of the fifthmagnetic layer 15 is higher than the saturation magnetization of the reference layer. Thereby, the stray magnetic field that is applied to the memory layer can be adjusted effectively by positioning the fifthmagnetic layer 15 to have a distance to the memory layer that is longer than that of the reference layer. - For example, the thickness of the reference layer is taken as tr; and the saturation magnetization of the reference layer is taken as Msr. The thickness of the fifth
magnetic layer 15 is taken as t5; and the saturation magnetization of the fifthmagnetic layer 15 is taken as Ms5. In such a case, for example, it is favorable for (Msr×tr) to be smaller than (Ms5×t5). The thickness of the secondmagnetic layer 12 is taken as t2; and the saturation magnetization of the secondmagnetic layer 12 is taken as Ms2. The thickness of the fourthmagnetic layer 14 is taken as t4; and the saturation magnetization of the fourthmagnetic layer 14 is taken as Ms4. In the example, the thickness (tr) of the reference layer is the sum of the thickness (t4) of the fourthmagnetic layer 14 and the thickness (t2) of the secondmagnetic layer 12. The magnetization amount (Msr×tr) of the reference layer is, for example, (Ms2×t2+Ms4×t4). - The fifth
magnetic layer 15 may be provided in combination with any reference layer. In such a case, for example, the reference layer is positioned between the fifthmagnetic layer 15 and the memory layer. The thirdnonmagnetic layer 13N may be provided between the fifthmagnetic layer 15 and the reference layer. -
FIG. 15 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 15 , themagnetoresistive element 111H according to the embodiment includes the thirdmagnetic layer 13, the fourthmagnetic layer 14, and the fifthmagnetic layer 15. - The first
magnetic layer 11 is provided between the fifthmagnetic layer 15 and the secondmagnetic layer 12. In the example, thebase layer 10S is provided between the fifthmagnetic layer 15 and the firstmagnetic layer 11. In the example as well, the firstnonmagnetic layer 11N is provided between the firstmagnetic layer 11 and the secondmagnetic layer 12. The thirdmagnetic layer 13 is provided between the firstmagnetic layer 11 and the firstnonmagnetic layer 11N. The fourthmagnetic layer 14 is provided between the secondmagnetic layer 12 and the firstnonmagnetic layer 11N. In the example, the firstmagnetic layer 11 is used as, for example, a reference layer. The secondmagnetic layer 12 is used as a memory layer. -
FIG. 16 is a schematic cross-sectional view showing another magnetoresistive element according to the first embodiment. - As shown in
FIG. 16 , the magnetoresistive element 111I according to the embodiment includes the thirdmagnetic layer 13, the fourthmagnetic layer 14, the fifthmagnetic layer 15, and the thirdnonmagnetic layer 13N. - The fifth
magnetic layer 15 is provided between thebase layer 10S and the secondmagnetic layer 12. The firstmagnetic layer 11 is provided between the fifthmagnetic layer 15 and the secondmagnetic layer 12. The thirdnonmagnetic layer 13N is provided between the fifthmagnetic layer 15 and the firstmagnetic layer 11. In the example as well, the firstnonmagnetic layer 11N is provided between the firstmagnetic layer 11 and the secondmagnetic layer 12. The thirdmagnetic layer 13 is provided between the firstmagnetic layer 11 and the firstnonmagnetic layer 11N. The fourthmagnetic layer 14 is provided between the secondmagnetic layer 12 and the firstnonmagnetic layer 11N. In the example, the firstmagnetic layer 11 is used as, for example, a reference layer. The secondmagnetic layer 12 is used as a memory layer. - In the
magnetoresistive elements 111G to 111I in which the fifthmagnetic layer 15 is provided, for example, the strength of the stray magnetic field applied to the memory layer from the fifth magnetic layer 15 (the shift adjustment layer) may be set to be substantially the same as the strength of the stray magnetic field applied to the memory layer from the reference layer. For example, the total magnetization amount of the shift adjustment layer is smaller than the total magnetization amount of the reference layer in the case where the distance between the memory layer and the shift adjustment layer is shorter than the distance between the memory layer and the reference layer. On the other hand, in the case where the distance between the memory layer and the shift adjustment layer is longer than the distance between the memory layer and the reference layer, the total magnetization amount of the shift adjustment layer is larger than the total magnetization amount of the reference layer. Thereby, an appropriate shift adjustment is obtained. - In the
magnetoresistive elements nonmagnetic layer 11N includes the inverse-spinel structure. Thereby, a high magnetoresistance ratio MR is obtained. Further, a low resistance area product RA is obtained. High reliability is obtained. - In the magnetoresistive elements (e.g., the
magnetoresistive elements magnetic layer 11 and the secondmagnetic layer 12. - Thereby, for example, it is possible to set the easy magnetization directions of these magnetic layers to be perpendicular to the film face.
- The state of being perpendicular to the film face corresponds to the state of being aligned with the Z-axis direction. The state of being parallel to the film face corresponds to the state of being aligned with one direction in the X-Y plane.
- For example, the magnetoresistive element according to the embodiment is an in-plane magnetization element (an in-plane magnetization MTJ element) or a perpendicular magnetization element (a perpendicular magnetization MTJ element). In the in-plane magnetization element, for example, the magnetization direction of the first
magnetic layer 11 and the magnetization direction of the secondmagnetic layer 12 are aligned with the film face. In the perpendicular magnetization element, for example, the magnetization of the firstmagnetic layer 11 and the magnetization of the secondmagnetic layer 12 are aligned with a direction perpendicular to the film face. - In a ferromagnet having a macro size, the internal energy is lowest when the spontaneous magnetization is oriented in its easy magnetization direction in the state of no external magnetic field. In the ferromagnet having the macro size, the internal energy is largest when the spontaneous magnetization is oriented in its hard magnetization direction in the state in which there is no external magnetic field.
- In a first example of the
magnetoresistive elements nonmagnetic layer 11N may not be an epitaxial layer in which the crystal orientation in the in-plane direction is uniform. For example, the firstnonmagnetic layer 11N may include an epitaxially grown monocrystal. Or, the firstnonmagnetic layer 11N may have a polycrystalline structure having the c-axis orientation. For example, the wave number selectivity of the tunneling electrons can be improved. A high magnetoresistance ratio MR can be obtained. - In a second example of the
magnetoresistive elements nonmagnetic layer 11N to be epitaxially grown. Thereby, the wave number selectivity of the tunneling electrons can be improved. A high magnetoresistance ratio MR is obtained. - In a third example of the
magnetoresistive elements nonmagnetic layer 11N to be epitaxially grown. Thereby, the wave number selectivity of the tunneling electrons can be improved. A high magnetoresistance ratio MR is obtained. - In the embodiment, the oxide included in the first
nonmagnetic layer 11N may include In and oxygen. In such a case as well, the oxide includes the inverse-spinel structure. In the embodiment, the oxide that is included in the firstnonmagnetic layer 11N may include Mg, Ga, In, and oxygen. In such a case as well, the oxide includes the inverse-spinel structure. - For example, at least one of the first
magnetic layer 11 or the secondmagnetic layer 12 includes at least one selected from the group consisting of Co and Fe. For example, at least one of the firstmagnetic layer 11 or the secondmagnetic layer 12 includes a first element and a second element. The first element is selected from the group consisting of Mn, Al, Ge, and Ga. The second element is selected from the group consisting of Mn, Al, Ge, and Ga and is different from the first element recited above. - At least one of the third
magnetic layer 13 or the fourthmagnetic layer 14 includes, for example, at least one selected from the group consisting of Co and Fe. - Examples of the materials, thicknesses, etc., of the layers included in the magnetoresistive element according to the embodiment will now be described.
- The
base layer 10S is, for example, a foundation layer. For example, the crystallinity of the other layers (for example, the firstmagnetic layer 11, etc.) is controlled by thebase layer 10S. The crystallinity includes, for example, the orientation of the crystal, the grain size of the crystal, etc. Thebase layer 10S is conductive or insulative. Thebase layer 10S includes a conductive material in the case where a current is caused to flow in thebase layer 10S. - In a first example of the
base layer 10S, thebase layer 10S has a NaCl structure having the (001) orientation. Thebase layer 10S includes a nitride. The nitride includes at least one selected from the group consisting of Ti, Zr, Nb, V, Hf, Ta, Mo, W, B, Al, and Ce. - In a second example of the
base layer 10S, thebase layer 10S includes a perovskite oxide layer. The perovskite oxide layer includes a perovskite oxide having the (002) orientation of ABO3. The site “A” includes at least one element selected from the group consisting of Sr, Ce, Dy, La, K, Ca, Na, Pb, and Ba. The site “B” includes at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Nb, Mo, Ru, Ir, Ta, Ce, and Pb. - In a third example of the
base layer 10S, thebase layer 10S includes a layer of an oxide. The layer of the oxide has a NaCl structure having the (001) orientation. The layer of the oxide includes at least one element selected from the group consisting of Mg, Al, and Ce. - In a fourth example of the
base layer 10S, thebase layer 10S includes a layer including at least one selected from the group consisting of Al, Cr, Ga, Fe, Co, Ni, Rh, Pd, Ag, Ir, Pt, Au, Mo, and W. The layer has a tetragonal crystal structure having the (001) orientation. Or, the layer has a cubic crystal structure having the (001) orientation. - In a fifth example of the
base layer 10S, thebase layer 10S has a stacked structure including any of the multiple layers of the first to fourth examples recited above. - For example, the crystallinities of the other layers can be controlled by the
base layer 10S of the first to fifth examples such as that recited above. Good characteristics are obtained. - The first
magnetic layer 11 has, for example, perpendicular magnetization. For example, a saturation magnetization Ms of the material (the magnetic material) of the firstmagnetic layer 11 is small. The material of the firstmagnetic layer 11 has, for example, a high magnetic anisotropy energy Ku. The material of the firstmagnetic layer 11 has, for example, a low Gilbert damping constant. For example, a high thermal stability is obtained. For example, the magnetization reversal is performed using a low current. For example, a thermal stability index Δ is maintained by the high magnetic anisotropy energy Ku. - In the case where the third
magnetic layer 13 is not used, it is favorable for the material of the firstmagnetic layer 11 to have a high polarization. - In a first example of the first
magnetic layer 11, the firstmagnetic layer 11 includes a magnetic layer including at least one selected from the group consisting of Co and Fe. The firstmagnetic layer 11 includes, for example, at least one selected from the group consisting of Co, Fe, CoFe, and CoFeB. - In a second example of the first
magnetic layer 11, the firstmagnetic layer 11 includes a magnetic layer including a Co-based Heusler alloy. The Co-based Heusler alloy is notated as Co2YZ. The firstmagnetic layer 11 includes at least one selected from the group consisting of Co2FeAl, Co2MnSi, Co2MnGe, Co2Mn(Si, Ge), and Co2Mn(Ga, Ge). - In the first and second examples recited above, the materials and the thicknesses are selected appropriately. Thereby, a perpendicular magnetic anisotropy is obtained in the first
magnetic layer 11. For example, the interface-perpendicular magnetic anisotropy is induced markedly by a certain thickness. The characteristics as a perpendicular magnetization film are obtained. - In a third example of the first
magnetic layer 11, the magnetic layer that is included in the firstmagnetic layer 11 includes Mn and a first element. The first element includes at least one selected from the group consisting of Al, Ge, and Ga. The firstmagnetic layer 11 includes at least one selected from the group consisting of MnGa, MnAl, MnGe, and MnAlGe. - In a fourth example of the first
magnetic layer 11, the firstmagnetic layer 11 includes Mn, Ga, and a first element. The first element includes at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy. The firstmagnetic layer 11 includes, for example, at least one selected from the group consisting of MnGaAl, MnGaGe, MnGaIr, MnGaCr, MnGaCo, MnGaPt, MnGaRu, MnGaPd, MnGaRh, MnGaNi, MnGaFe, MnGaRe, MnGaAu, MnGaCu, MnGaB, MnGaC, MnGaP, MnGaGd, MnGaTb, and MnGaDy. - In the third and fourth examples of the first
magnetic layer 11 recited above, for example, the firstmagnetic layer 11 is grown so that the c-axis is perpendicular to the film face. For example, the firstmagnetic layer 11 is grown to have the (001) orientation. Thereby, for example, a perpendicular magnetic anisotropy is obtained. For example, thebase layer 10S is selected appropriately. Thereby, the crystal orientation growth of the firstmagnetic layer 11 can be controlled. - In a fifth example of the first
magnetic layer 11, the firstmagnetic layer 11 includes an alloy. The alloy includes a first element and a second element. The first element includes, for example, at least one selected from the group consisting of Fe, Co, and Ni. The second element includes at least one selected from the group consisting of Ru, Rh, Pd, Ag, Ir, Pt, and Au. Or, the firstmagnetic layer 11 may include a stacked body. The stacked body includes, for example, at least one selected from the group consisting of a Co/Pt artificial lattice, a Co/Pd artificial lattice, a Co/Ru artificial lattice, a Co/Ir artificial lattice, and a Co/Au artificial lattice. In these artificial lattices, the addition of elements and the ratios of the thicknesses of the magnetic layers and the nonmagnetic layers are adjusted. Thereby, for example, the perpendicular magnetic anisotropy and the saturation magnetization are adjusted. The alloy recited above may include, for example, at least one selected from the group consisting of FeRh, FePt, FePd, CoPt, and CoPd. The alloy is, for example, a ferromagnetic alloy. - In a sixth example of the first
magnetic layer 11, the firstmagnetic layer 11 includes an oxide. The oxide includes at least one selected from the group consisting of Mn, Co, Ni, Cu, Zn, and Fe. The firstmagnetic layer 11 includes, for example, at least one selected from the group consisting of Fe3O4, MnFe2O4, CoFe2O4, NiFe2O4, CuFe2O4, and ZnFe2O4. The firstmagnetic layer 11 includes, for example, a mixed crystal including at least two selected from the group recited above. The group of the materials recited above is, for example, a ferrite having a spinel crystal structure. In the case where the group of the materials recited above is included in the firstmagnetic layer 11, the firstmagnetic layer 11 has the same crystal symmetry as the firstnonmagnetic layer 11N. Therefore, good matching properties are obtained. For example, an interface that has high crystal quality and high compatibility is obtained. For example, an interface that has substantially no dislocations is obtained. For example, magnetite (Fe3O4) is a metallic oxide and has half-metallic properties. The Gilbert damping constant of magnetite (Fe3O4) is low. Magnetite (Fe3O4) is applied particularly favorably to the firstmagnetic layer 11. - It is favorable for the thickness of the first
magnetic layer 11 to be thin. The thickness (the length along the Z-axis direction) of the firstmagnetic layer 11 is, for example, not less than 1 nm and not more than 5 nm. Thereby, for example, magnetization reversal is obtained using a low current. For example, in a crystalline material in which a high thermal stability index Δ is obtained due to the magneto-crystalline anisotropy, there are cases where the anisotropy decreases if the thickness is thin. In the case where such a crystalline material is used, it is favorable for the thickness of the firstmagnetic layer 11 to be 10 nm or less. - Examples of the third
magnetic layer 13 and the fourthmagnetic layer 14 will now be described. Hereinbelow, these magnetic layers are called the “intermediate magnetic layer” for convenience. The “intermediate magnetic layer” refers to at least one of the thirdmagnetic layer 13 or the fourthmagnetic layer 14. - The intermediate magnetic layer is, for example, a perpendicular magnetization film. The intermediate magnetic layer has, for example, a high magnetic anisotropy energy Ku. The intermediate magnetic layer has a high polarization. For example, a high thermal stability index Δ is maintained by the high magnetic anisotropy energy Ku. In the case where the intermediate magnetic layer functions as the intermediate magnetic layer on the reference layer side, it is favorable for the saturation magnetization of the intermediate magnetic layer to be low. Thereby, the stray magnetic field into the memory layer can be reduced. On the other hand, in the case where the intermediate magnetic layer functions as the intermediate magnetic layer on the memory layer side, it is favorable for the Gilbert damping constant of the intermediate magnetic layer to be low. Thereby, for example, the magnetization reversal due to the current is easy.
- As a first example of the intermediate magnetic layer, the intermediate magnetic layer includes an alloy. The alloy includes at least one selected from the group consisting of Fe and Co. The intermediate magnetic layer may include at least one element selected from the group consisting of Ni, B, C, P, Ta, Ti, Mo, Si, W, Nb, Mn, Al, and Ge. For example, the saturation magnetization of the intermediate magnetic layer can be controlled. For example, the alloy that is included in the intermediate magnetic layer may include a first element and a second element. The first element includes at least one selected from the group consisting of Fe and Co. The second element includes at least one selected from the group consisting of Ni, B, C, P, Ta, Ti, Mo, Si, W, Nb, Mn, Al, and Ge. The intermediate magnetic layer includes, for example, CoFeB. The intermediate magnetic layer may include, for example, at least one selected from the group consisting of CoFeSi, CoFeP, CoFeW, and CoFeNb. These alloys have a spin polarization that is equal to that of CoFeB. The intermediate magnetic layer may include, for example, Heusler alloys. The Heusler alloys include, for example, at least one selected from the group consisting of Co2FeSi, Co2MnSi, Co2MnGe, Co2MnAl, Co2FeAl, Co2(Fe, Mn) Si, and Co2(Fe, Mn) Al. The Heusler alloys have, for example, a spin polarization that is equal to or higher than that of CoFeB. The Heusler alloys are suited to the intermediate magnetic layer.
- In a second example of the intermediate magnetic layer, the intermediate magnetic layer includes an oxide. The oxide includes at least one selected from the group consisting of Mn, Co, Ni, Cu, Zn, and Fe. The intermediate magnetic layer includes, for example, at least one selected from the group consisting of Fe3O4, MnFe2O4, CoFe2O4, NiFe2O4, CuFe2O4, and ZnFe2O4. The intermediate magnetic layer may include a mixed crystal including two or more selected from the group of the materials recited above. The group of the materials recited above is, for example, a ferrite having a spinel crystal structure. The ferrite that has the spinel crystal structure has the same crystal symmetry as the first
nonmagnetic layer 11N. For example, the ferrite that has the spinel crystal structure has excellent matching properties. For example, high crystal quality is obtained. For example, an interface that has substantially no dislocations is obtained. Magnetite (Fe3O4) is a metallic oxide and has half-metallic properties. Magnetite (Fe3O4) has a low Gilbert damping constant. Magnetite (Fe3O4) is applied particularly favorably to the intermediate magnetic layer. - In a third example of the intermediate magnetic layer, the intermediate magnetic layer includes a MnGa alloy. In the example, the intermediate magnetic layer may further include at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy. For example, at least one of the saturation magnetization, the perpendicular magnetic anisotropy, the Gilbert damping constant, or the spin polarization is controlled. The intermediate magnetic layer includes, for example, MnGaX. The MnGaX includes Mn, Ga, and a first element. The first element (X) includes at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy. The intermediate magnetic layer includes, for example, at least one selected from the group consisting of MnGaAl, MnGaGe, MnGaIr, MnGaCr, MnGaCo, MnGaPt, MnGaRu, MnGaPd, MnGaRh, MnGaNi, MnGaFe, MnGaRe, MnGaAu, MnGaCu, MnGaB, MnGaC, MnGaP, MnGaGd, MnGaTb, and MnGaDy.
- In a fourth example of the intermediate magnetic layer, the intermediate magnetic layer includes a MnGe alloy. In the MnGe alloy, for example, in the (001) direction, one state of the spin band is positioned at the Fermi level vicinity. It is considered that the MnGe alloy has half-metallic characteristics for this crystal orientation. For example, the spin polarization of the MnGe alloy can be improved. By applying the MnGe alloy, a high magnetoresistance ratio MR is obtained.
- In a fifth example of the intermediate magnetic layer, the intermediate magnetic layer includes an alloy. The alloy includes a first element, a second element, and a third element. The first element includes at least one selected from the group consisting of Mn, Fe, Co, and Ni. The second element includes at least one selected from the group consisting of Zn, Al, Ga, In, Si, Ge, Sn, As, Sb, and Bi. The third element includes at least one selected from the group consisting of Zn, Al, Ga, In, Si, Ge, Sn, As, Sb, and Bi. The third element is different from the second element. The intermediate magnetic layer includes, for example, at least one selected from the group consisting of MnAlGe and MnZnSb.
- In a sixth example of the intermediate magnetic layer, the intermediate layer includes a MnAl alloy. The MnAl alloy includes a light element. The Gilbert damping constant of the MnAl alloy is small. For example, the energy that is necessary for the magnetization reversal is low. For example, the current density necessary for the spin-polarized electrons to reverse the magnetization can be reduced drastically. Similarly to the MnGe alloy, the MnAl alloy has half-metallic characteristics in the (001) direction. The MnAl alloy has a high spin polarization. By using the MnAl alloy, for example, a high magnetoresistance ratio MR is obtained.
- For the MnGa, the MnGaX, the MnGe, the MnAlGe, the MnZnSb, the MnAl, etc., of the intermediate magnetic layer shown in the third to sixth examples recited above, the characteristics as a magnetization film are obtained in the appropriate composition range. For example, the intermediate magnetic layer is oriented so that the c-axis is perpendicular to the film face. For example, the intermediate magnetic layer is grown to have the (001) orientation. Thereby, a perpendicular magnetic anisotropy is obtained. For example, in the case where the intermediate magnetic layer is formed on the first
magnetic layer 11, the firstmagnetic layer 11 is selected appropriately. For example, in the case where the intermediate magnetic layer is formed on the firstnonmagnetic layer 11N, the firstnonmagnetic layer 11N is selected appropriately. For example, the crystal orientation growth of the intermediate magnetic layer can be controlled by the layer positioned under the intermediate magnetic layer when forming the intermediate magnetic layer. - Generally, the Gilbert damping constant of the magnetic material has a correlation with the magnitude of the spin-orbit coupling of the magnetic material. For example, the spin-orbit coupling is large for materials including an element having a large atomic number. In the material that includes the element having the large atomic number, generally, the Gilbert damping constant is large. The magnetic material of the example recited above includes a relatively light element. Therefore, the Gilbert damping constant is small. The energy that is necessary for the magnetization reversal is low. For example, the current density necessary for the spin-polarized electrons to reverse the magnetization can be reduced drastically. The magnetic material of the example recited above is applicable particularly effectively to the intermediate magnetic layer on the memory layer side.
- For example, the third
magnetic layer 13 or the fourthmagnetic layer 14 is epitaxially grown from the firstnonmagnetic layer 11N. Thereby, a high magnetoresistance ratio MR is obtained. For example, in the intermediate magnetic layer that contacts the firstnonmagnetic layer 11N, the lattice length along the X-Y plane may be shifted from the unique lattice constant of the material. - The first
nonmagnetic layer 11N functions as, for example, a tunneling barrier layer. - The first
nonmagnetic layer 11N is crystalline. The firstnonmagnetic layer 11N includes, for example, a monocrystal. The firstnonmagnetic layer 11N may include a polycrystal. The firstnonmagnetic layer 11N may include an amorphous region. By the firstnonmagnetic layer 11N being crystalline, for example, scattering of the electrons in the firstnonmagnetic layer 11N is suppressed. For example, the probability of selective tunneling conduction of the electrons while storing the wave number increases. Thereby, a high magnetoresistance ratio MR is obtained easily. Accordingly, from the perspective of obtaining a large magnetoresistance ratio MR, it is more favorable for the tunneling barrier layer to be a monocrystal than a polycrystal (including an alignment film). - In a first example of the first
nonmagnetic layer 11N, the firstnonmagnetic layer 11N includes an oxide. The oxide includes Mg and Ga. The firstnonmagnetic layer 11N includes, for example, MgGa2O4. The bandgap of MgGa2O4 is about 4.7 eV. Thereby, a low resistance area product RA is obtained. The lattice constant of MgGa2O4 is 0.8286 nm. For example, the lattice mismatch between MgGa2O4 and Fe is about 2.2%. The lattice mismatch between MgGa2O4 and MnGa is about 6.4%. MgGa2O4 has good lattice matching with many ferromagnetic materials. - The composition ratios of the elements of “MgGa2O4” may not be exact. For example, the compositions of Mg, Ga, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained. MgGa2O4 may not be a perfect cubic crystal. For example, tetragonal distortion of 10% or less may be included.
- In the experimental results described in reference to
FIG. 2 , Fe is used as the firstmagnetic layer 11 and the secondmagnetic layer 12. In the case where a MgGa2O4 layer is used with the Fe layer, it is considered that a band-folding effect arises because the in-plane lattice constants are different. For example, there is a possibility that the effective spin polarization of the A band of Fe may decrease due to the band-folding effect. If the decrease of the effective spin polarization is suppressed, a higher magnetoresistance ratio MR is obtained. - For example, in the case where the magnetic layer that is in directly contact with the MgGa2O4 is half-metallic, the band-folding effect can be substantially ignored. For example, in the case where the magnetic layer is a half-metallic Heusler alloy, etc., it is considered that a magnetoresistance ratio MR that is even higher than the magnetoresistance ratio MR of the experimental results described in reference to
FIG. 2 is obtained. - In the embodiment, for example, it is favorable for the magnetic layers (the first to fourth
magnetic layers 11 to 14, etc.) that are in directly contact with the firstnonmagnetic layer 11N to include Heusler alloys. - In a second example of the first
nonmagnetic layer 11N, the oxide included in the firstnonmagnetic layer 11N includes Mg, Ga, and In. The firstnonmagnetic layer 11N includes, for example, Mg(Ga, In)2O4, etc. - The compositions of the elements of “Mg(Ga, In)2O4” may not be exact. For example, the compositions of Mg, Ga, In, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- The spinel inversion degree is high for MgGa2O4 and MgIn2O4. For example, it is considered that the inverse-spinel structure is stable for MgIn2O4.
- For example, the first
nonmagnetic layer 11N may include MgGa2O4 (the main material) and In. In has a low melting point and a large ionic radius. By using such In, the spinel inversion degree can be increased. - The bandgap of MgIn2O4 is smaller than the bandgap of MgGa2O4. For example, the first
nonmagnetic layer 11N may include MgGa2O4 (the main material) and In. For example, a small bandgap is obtained. It is favorable for the oxide of the firstnonmagnetic layer 11N to include Mg, Ga, and In. The inverse-spinel structure is more stable; and a small bandgap is obtained. - In a third example of the first
nonmagnetic layer 11N, the oxide included in the firstnonmagnetic layer 11N includes In. The firstnonmagnetic layer 11N includes, for example, at least one selected from the group consisting of MgIn2O4, ZnIn2O4, and (Mg, Zn)In2O4. - The compositions of the elements of “MgIn2O4” recited above may not be exact. For example, the compositions of Mg, In, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- A main group element metal may be further included in the material of the first
nonmagnetic layer 11N described in reference to the first to third examples recited above. The main group element is an element that forms a spinel structure. The content of the main group element is, for example, 10 atm % (atomic percent) or less. Thereby, the inverse-spinel structure substantially does not degrade. Such a main group element metal includes, for example, at least one selected from the group consisting of Zn, Cd, Al, Si, Ge, and Sn. For example, a portion of the elements included in the inverse-spinel structure may be replaced with such a main group metal element. For example, the bandgap, the phase stability, and the lattice constant are adjusted. - In a fourth example of the first
nonmagnetic layer 11N, the firstnonmagnetic layer 11N includes two or more layers of the materials described in reference to the first to third examples recited above. These layers are stacked. The first layer that is included in the stacked structure contacts, for example, the magnetic layer (the first to fourthmagnetic layers 11 to 14, etc.). The second layer that is included in the stacked structure does not contact a magnetic layer. For example, the lattice matching of the first layer with the magnetic layer recited above is good. For example, the bandgap of the second layer is low. By such a configuration, for example, a high magnetoresistance ratio MR and a low resistance area product RA are obtained. The firstnonmagnetic layer 11N includes, for example, at least one selected from the group consisting of MgIn2O4/MgGa2O4, Mg(Ga, In)2O4/MgGa2O4, MgGa2O4/MgIn2O4/MgGa2O4, and MgGa2O4/Mg(Ga, In)2O4/MgGa2O4. - The compositions of the elements of “AB2O4” recited above may not be exact. For example, the compositions of the elements of A, B, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- In a fifth example of the first
nonmagnetic layer 11N, the firstnonmagnetic layer 11N includes a first compound layer and a first layer. The first compound layer is one of MgO or MgAl2O4. The first layer is stacked with the first compound layer. The first layer includes the materials described in reference to the first to third examples recited above. The first compound layer contacts, for example, a magnetic layer (the first to fourthmagnetic layers 11 to 14, etc.). The first layer does not contact a magnetic layer. By such a configuration, for example, a high magnetoresistance ratio MR and a low resistance area product RA are obtained. For the first compound, for example, a high magnetoresistance ratio MR is obtained. A low resistance area product RA is obtained for the first layer including the materials shown in the first to third examples recited above. The firstnonmagnetic layer 11N includes, for example, at least one selected from the group consisting of MgGa2O4/MgO, MgGa2O4/MgAl2O4, MgO/MgGa2O4/MgO, MgAl2O4/MgGa2O4/MgAl2O4, MgIn2O4/MgO, MgIn2O4/MgAl2O4, MgO/MgIn2O4/MgO, MgAl2O4/MgIn2O4/MgAl2O4, Mg(Ga, In)2O4/MgO, Mg(Ga, In)2O4/MgAl2O4, MgO/Mg(Ga, In)2O4/MgO, and MgAl2O4/Mg(Ga, In)2O4/MgAl2O4. - The compositions of the elements of “MgO” recited above may not be exact. For example, the compositions of the elements of Mg and O may be adjusted in the ranges in which the rock-salt structure can be maintained. The compositions of the elements of “AB2O4” recited above may not be exact. For example, the compositions of the elements A, B, and O may be adjusted in ranges in which the inverse-spinel structure can be maintained.
- The second
magnetic layer 12 has, for example, a perpendicular magnetization. The secondmagnetic layer 12 has, for example, a high magnetic anisotropy energy Ku. The secondmagnetic layer 12 has, for example, at least one of a coercivity that is larger than the coercivity of the firstmagnetic layer 11, an anisotropic magnetic field that is larger than the anisotropic magnetic field of the firstmagnetic layer 11, or a Gilbert damping constant that is larger than the Gilbert damping constant of the firstmagnetic layer 11. For example, the thermal stability index Δ can be maintained by the high magnetic anisotropy energy Ku. It is favorable for the saturation magnetization Ms of the secondmagnetic layer 12 to be small. Thereby, for example, the effects of the stray magnetic field from the reference layer can be reduced. It is favorable for the polarization of the secondmagnetic layer 12 to be high. Thereby, for example, a high magnetoresistance ratio MR is obtained. - In a first example of the second
magnetic layer 12, the secondmagnetic layer 12 includes Mn and a first element. The first element includes at least one selected from Al, Ge, and Ga. The secondmagnetic layer 12 includes at least one selected from the group consisting of MnGa, MnAl, MnGe, and MnAlGe. - In a second example of the second
magnetic layer 12, the secondmagnetic layer 12 includes Mn, Ga, and a first element. The first element includes at least one selected from the group consisting of Al, Ge, Ir, Cr, Co, Pt, Ru, Pd, Rh, Ni, Fe, Re, Au, Cu, B, C, P, Gd, Tb, and Dy. The secondmagnetic layer 12 includes, for example, at least one selected from the group consisting of MnGaAl, MnGaGe, MnGaIr, MnGaCr, MnGaCo, MnGaPt, MnGaRu, MnGaPd, MnGaRh, MnGaNi, MnGaFe, MnGaRe, MnGaAu, MnGaCu, MnGaB, MnGaC, MnGaP, MnGaGd, MnGaTb, and MnGaDy. - For example, at least one of the first
nonmagnetic layer 11N or the fourthmagnetic layer 14 is selected appropriately. Thereby, for example, the crystal orientation growth of the secondmagnetic layer 12 can be controlled. For example, in the secondmagnetic layer 12, the c-axis is in a direction perpendicular to the film face. For example, in the secondmagnetic layer 12, growth in the (001) orientation is obtained. For example, a perpendicular magnetic anisotropy is obtained. - In a third example of the second
magnetic layer 12, the secondmagnetic layer 12 includes an alloy. The crystal of at least a portion of the alloy is oriented in, for example, (111) of a face-centered cubic structure (FCC). Or, the crystal of at least a portion of the alloy is oriented in (0001) of a hexagonal close-packed structure (HCP). The alloy that is included in the secondmagnetic layer 12 may form, for example, an artificial lattice. - For example, the alloy recited above that has the crystal orientation of (111) of FCC or (0001) of HCP includes, for example, a first element and a second element. The first element includes at least one selected from the group consisting of Fe, Co, Ni, and Cu. The second element includes at least one selected from the group consisting of Pt, Pd, Rh, and Au. The alloy that is included in the second
magnetic layer 12 is, for example, a ferromagnetic alloy. The ferromagnetic alloy includes, for example, at least one selected from the group consisting of CoPd, CoPt, NiCo, and NiPt. - The alloy recited above that is included in the second
magnetic layer 12 and may form the artificial lattice includes, for example, a first layer and a second layer stacked alternately. The first layer includes, for example, an alloy (a ferromagnetic film) including one element selected from the group consisting of Fe, Co, and Ni. The second layer includes, for example, an alloy (a nonmagnetic film) including one element selected from the group consisting of Cr, Pt, Pd, Jr, Rh, Ru, Os, Re, Au, and Cu. The secondmagnetic layer 12 includes, for example, at least one selected from the group consisting of a Co/Pt artificial lattice, a Co/Pd artificial lattice, a CoCr/Pt artificial lattice, a Co/Ru artificial lattice, a Co/Ir artificial lattice, a Co/Os artificial lattice, a Co/Au artificial lattice, and a Ni/Cu artificial lattice. In these artificial lattices, at least one of the addition of an element to the ferromagnetic film or the ratio of the thicknesses of the ferromagnetic film and the nonmagnetic film is adjusted. At least one of the perpendicular magnetic anisotropy or the saturation magnetization can be adjusted. - In a fourth example of the second
magnetic layer 12, the secondmagnetic layer 12 includes an alloy. The alloy includes a first element and a second element. The first element includes at least one selected from the group consisting of Fe, Co, and Ni. The first element is, for example, a transition metal. The second element includes, for example, at least one selected from the group consisting of Tb, Dy, and Gd. The second element is, for example, a rare-earth metal. The secondmagnetic layer 12 includes, for example, at least one selected from the group consisting of TbFe, TbCo, TbFeCo, DyTbFeCo, and GdTbCo. The secondmagnetic layer 12 may include a stacked body. The stacked body includes multiple layers. Each of the multiple layers includes the alloys recited above. Multiple types of layers may be stacked alternately in the stacked body. The secondmagnetic layer 12 may include, for example, at least one stacked body selected from the group consisting of TbFe/Co, TbCo/Fe, TbFeCo/CoFe, DyFe/Co, DyCo/Fe, and DyFeCo/CoFe. For example, at least one of the thickness or the composition is adjusted for these alloys. For example, at least one of the perpendicular magnetic anisotropy or the saturation magnetization is adjusted. - In a fifth example of the second
magnetic layer 12, the secondmagnetic layer 12 includes an alloy. The alloy includes a first element and a second element. The first element includes at least one selected from the group consisting of Fe, Co, Ni, and Cu. The second element includes at least one selected from the group consisting of Pt, Pd, Rh, and Au. The secondmagnetic layer 12 includes, for example, a ferromagnetic alloy. The ferromagnetic alloy includes at least one selected from the group consisting of FeRh, FePt, FePd, CoPt, and CoPd. - Examples of the first
intermediate layer 21 and the secondintermediate layer 22 will now be described. Hereinbelow, these layers are called the “intermediate layer” for convenience. The “intermediate layer” refers to at least one of the firstintermediate layer 21 or the secondintermediate layer 22. It is favorable for the intermediate layer to include a nonmagnetic material. - For example, mixing due to the element diffusion between the first
magnetic layer 11 and the thirdmagnetic layer 13 is suppressed by the intermediate layer. For example, mixing due to the element diffusion between the secondmagnetic layer 12 and the fourthmagnetic layer 14 is suppressed by the intermediate layer. - For example, the elements that are included in the intermediate layer and the elements that are included in the magnetic layer may not form a solid solution with each other. Or, the elements that are included in the intermediate layer and the elements that are included in the magnetic layer may form a substantially completely intermetallic compound. The mixing is suppressed. For example, a better effect of repelling hetero elements occurs in the intermediate layer. For example, diffusion is suppressed in the intermediate layer. For example, it is favorable for the intermediate layer to have high heating tolerance. It is favorable for the intermediate layer to include a refractory material. For example, it is favorable for the nonmagnetic layer that is included in the intermediate layer to include at least one element selected from the group consisting of Mg, Ba, Ca, Sr, Sc, Y, Ta, W, Nb, Gd, Tb, Dy, Ce, Ho, Yb, Er, B, C, and N. The intermediate layer may include a compound including the elements recited above. For example, the melting point is increased by the compound. For example, the intermediate layer includes at least one selected from the group consisting of a boride including the elements recited above, a carbide including the elements recited above, and a nitride including the elements recited above. The intermediate layer may include a stacked body. The stacked body includes multiple layers including the elements recited above. The stacked body includes multiple layers including the compounds recited above.
- In the case where the intermediate layer is provided between two layers and the crystal structures of the two layers are similar to each other, it is favorable for the intermediate layer to be crystalline. For example, it is favorable for the compatibility of the crystal type and the lattice constant of the intermediate layer with the two layers to be good. Thereby, for example, the function of the intermediate layer as a lattice buffer layer increases. On the other hand, in the case where the intermediate layer is provided between two layers and the crystal structures of the two layers are different from each other, it is favorable for the intermediate layer to have an amorphous state. By the intermediate layer having an amorphous state, for example, the desired orientation state is easier to obtain in at least one of the two layers. In the amorphous state of the intermediate layer, for example, there is no long range order (periodic structure) such as that of a crystal. The amorphous state of the intermediate layer may have short range order. The amorphous state of the intermediate layer may include a polycrystal having an average crystal grain of 2 nm or less.
- It is favorable for the thickness of the intermediate layer to be, for example, not less than 0.1 nm and not more than 2 nm. For example, in the case where the thickness is 0.1 nm or more, the suppression of the element diffusion in the two layers having the intermediate layer interposed is obtained effectively. In the case where the thickness is 2 nm or less, for example, the magnetic coupling of the two layers having the intermediate layer interposed is maintained.
- An example of a method for manufacturing the first
nonmagnetic layer 11N will now be described. - For example, a vapor phase epitaxy process is used in at least a portion of the formation of, for example, the oxide included in the first
nonmagnetic layer 11N. The vapor phase epitaxy process includes, for example, at least one of sputtering, MBE, or laser ablation. For example, in a first manufacturing method, after forming the alloy layer, the oxide layer is formed by various oxidation processes. The oxidation processes include, for example, the flow of an oxygen gas. The oxidation processes may include, for example, at least one of a plasma oxidation process or a radical oxidation process. A temperature, a processing time, and a power that are suited to the material and thickness of the alloy layer used to form the firstnonmagnetic layer 11N are applied. In a second manufacturing method, the formation of a film is performed using an oxide target. For example, the second manufacturing method is suitable in the case where the differences of the oxidizing capabilities and the melting points are large for the element of “A” and the element of “B” included in the spinel-structure oxide (e.g., AB2O4). In either manufacturing method, at least one of heating film formation or post-heating may be implemented. For example, the firstnonmagnetic layer 11N that has a higher crystallinity is obtained. - As described above, the oxide included in the first
nonmagnetic layer 11N (e.g., MgGa2O4) is formed by, for example, sputtering at room temperature. Subsequently, heat treatment is performed at, for example, not less than 300° C. and not more than 600° C. The temperature of the heat treatment may be not less than 400° C. and not more than 500° C. By the heat treatment, high crystallinity and good flatness are obtained. Oxygen may desorb due to the heat treatment. For example, an oxygen gas, etc., may be introduced in the heat treatment or after the heat treatment. Thereby, the desorption of the oxygen can be suppressed. - The embodiment relates to a magnetic memory device.
-
FIG. 17 is a schematic cross-sectional view illustrating the magnetic memory device according to the second embodiment. - As shown in
FIG. 17 , themagnetic memory device 210 according to the embodiment includes, for example, acontrol element 75 and the magnetoresistive element according to the first embodiment. Any magnetoresistive element according to the first embodiment or any magnetoresistive element of a modification according to the first embodiment may be used. In the example, themagnetoresistive element 111 is used. - The
control element 75 is electrically connected to themagnetoresistive element 111. In the example, thecontrol element 75 includes atransistor 70T. - A first
conductive layer 11E and a secondconductive layer 12E are provided in the example. These conductive layers are, for example, electrodes. The firstmagnetic layer 11, the secondmagnetic layer 12, and the firstnonmagnetic layer 11N are provided between these conductive layers. The firstconductive layer 11E is electrically connected to the firstmagnetic layer 11. The secondconductive layer 12E is electrically connected to the secondmagnetic layer 12. - A
first interconnect 70 a and asecond interconnect 70 b are provided in the example. Thefirst interconnect 70 a is electrically connected to the first magnetic layer 11 (in the example, the firstconductive layer 11E). Thesecond interconnect 70 b is electrically connected to the second magnetic layer 12 (in the example, the secondconductive layer 12E). For example, thesecond interconnect 70 b is one bit line. A drain 70Td of thetransistor 70T is electrically connected to thefirst interconnect 70 a via aconnection portion 78 a. A source 70Ts of thetransistor 70T is electrically connected to anotherinterconnect 78 c via aconnection portion 78 b. Theother interconnect 78 c is, for example, another bit line. A gate 70Tg of thetransistor 70T corresponds to a word line. In the example, thetransistor 70T is provided in a portion of asemiconductor substrate 70S. Thetransistor 70T functions as, for example, a selection transistor. Aninter-layer insulating portion 701 is provided around thetransistor 70T, the interconnects, the connection portions, etc. - At least one of the interconnect, the conductive layer, or the connection portion recited above includes, for example, at least one selected from the group consisting of W, Al, AlCu, and Cu.
- As described below, multiple magnetoresistive elements 111 (memory cells) are provided. One
control element 75 is electrically connected to one of the multiplemagnetoresistive elements 111. For example, the one of the multiplemagnetoresistive elements 111 is selected by thecontrol element 75. - An example of a method for manufacturing the magnetic memory device according to the embodiment will now be described. The manufacturing method of the example recited below includes a bonding process.
-
FIG. 18A toFIG. 18E are schematic cross-sectional views illustrating the method for manufacturing the magnetic memory device according to the second embodiment. - A first stacked body SB1 is prepared as shown in
FIG. 18A . The first stacked body SB1 includes any magnetoresistive element according to the first embodiment. Themagnetoresistive element 111 is provided in the example. Themagnetoresistive element 111 is provided on asubstrate 25 in the example. Thefirst substrate 25 is a monocrystalline substrate of silicon. Afirst bonding layer 25 a is provided on themagnetoresistive element 111. - For example, the layers that are included in the
magnetoresistive element 111 are formed on thesubstrate 25. The formation includes, for example, implementing at least one of sputtering or MBE (Molecular Beam Epitaxy). The appropriate conditions are applied to themagnetoresistive element 111. For example, crystallinity that reflects the silicon monocrystal crystallinity of thesubstrate 25 may be provided in the layers included in themagnetoresistive element 111. For example, at least one layer included in themagnetoresistive element 111 is caused to be substantially monocrystalline. - A second stacked body SB2 is prepared as shown in
FIG. 18B . The second stacked body SB2 includes, for example, thesemiconductor substrate 70S, thetransistor 70T, the connection portions (referring toFIG. 17 ), theinter-layer insulating portion 701, and asecond bonding layer 25 b. Thesecond bonding layer 25 b is provided on thetransistor 70T, the connection portions, and theinter-layer insulating portion 701. - The
first bonding layer 25 a and thesecond bonding layer 25 b include metals. The metals include, for example, at least one selected from the group consisting of Al, Au, Cu, Ti, and Ta. - As shown in
FIG. 18C , thefirst bonding layer 25 a and thesecond bonding layer 25 b are caused to oppose each other. For example, at least one of heating or the application of pressure is performed. Thefirst bonding layer 25 a and thesecond bonding layer 25 b are bonded to each other. - A portion of the
substrate 25 is removed as shown inFIG. 18D . For example, BSG (Back Side Grinder) processing is performed. Thereby, the thickness of thesubstrate 25 is reduced. - The remaining portion of the
substrate 25 is removed as shown inFIG. 18E . For example, CMP (Chemical Mechanical Polishing) processing is performed. - Subsequently, the interconnects, etc., are formed; and the
magnetic memory device 210 is made. - In the manufacturing method recited above, the first stacked body SB1 that includes the
magnetoresistive element 111 and the second stacked body SB2 that includes thetransistor 70T (the control element 75) are prepared separately. These stacked bodies are bonded. Therefore, the appropriate conditions (including the conditions relating to heat) are applied to each of the two stacked bodies. Thereby, good characteristics are obtained for the elements (themagnetoresistive element 111, thetransistor 70T, etc.) included in each of the stacked bodies. For example, good crystallinity is obtained for the layers. For example, good amorphousness is obtained for the layers. -
FIG. 19 is a schematic view illustrating the magnetic memory device according to the second embodiment. - As shown in
FIG. 19 , themagnetic memory device 220 according to the embodiment includes, for example, acontroller 70 and the magnetoresistive element according to the first embodiment. Any magnetoresistive element according to the first embodiment or any magnetoresistive element of a modification according to the first embodiment may be used. In the example, themagnetoresistive element 110 is used. - The
controller 70 is electrically connected to themagnetoresistive element 110. In the example, thefirst interconnect 70 a electrically connects thecontroller 70 and the first magnetic layer 11 (in the example, the firstconductive layer 11E) to each other. Thesecond interconnect 70 b electrically connects thecontroller 70 and the second magnetic layer 12 (in the example, the secondconductive layer 12E) to each other. Thecontrol element 75 described above may be provided on the path of the electrical connection. - For example, the
controller 70 can sense a value (e.g., at least one of a current, a voltage, or a resistance) corresponding to the electrical resistance of themagnetoresistive element 110. For example, thecontroller 70 reads information stored in themagnetoresistive element 110. Thecontroller 70 implements, for example, a read operation. - For example, the
controller 70 may apply external energy (a current, a voltage, an electric field, a magnetic field, etc.) to themagnetoresistive element 110. Multiple states may be formed in themagnetoresistive element 110 by the external energy. The electrical resistance of themagnetoresistive element 110 is different between the multiple states. For example, the multiple states correspond to the information that is stored. For example, a write operation and an erase operation may be implemented. -
FIG. 20 is a schematic view illustrating a magnetic memory device according to the second embodiment. - As shown in
FIG. 20 , themagnetic memory device 230 according to the embodiment includes multiple memory cells MC and thecontroller 70. - One of the multiple memory cells MC includes at least one magnetoresistive element and at least one
control element 75. The at least one magnetoresistive element is any magnetoresistive element or a modification of a magnetoresistive element according to the first embodiment. Themagnetoresistive element 110 is provided in the example. A first terminal of thecontrol element 75 is electrically connected to one end of themagnetoresistive element 110. Thecontrol element 75 corresponds to, for example, thetransistor 70T. The first terminal corresponds to, for example, the drain 70Td of thetransistor 70T. - Multiple bit lines BL1, multiple bit lines BL2, and multiple word lines WL are provided. In the example, the multiple bit lines BL1 and BL2 extend in the Y-axis direction. The multiple bit lines BL1 and BL2 are arranged in the X-axis direction. The multiple word lines WL extend in the X-axis direction. The multiple word lines WL are arranged in the Y-axis direction.
- The other end of the
magnetoresistive element 110 included in the one of the multiple memory cells MC is electrically connected to one of the multiple bit lines BL1. A second terminal of thecontrol element 75 included in the one of the multiple memory cells MC is electrically connected to one of the multiple bit lines BL2. The second terminal corresponds to, for example, the source 70Ts of thetransistor 70T. - A third terminal of the
control element 75 included in the one of the multiple memory cells MC is electrically connected to one of the multiple word lines WL. The third terminal of thecontrol element 75 is electrically connected. The third terminal corresponds to, for example, the gate 70Tg of thetransistor 70T. - Each of the multiple bit lines BL1 is connected to a first current source/sink circuit SSC1 via a first switch SW1. Each of the multiple bit lines BL2 is connected to a second current source/sink circuit SSC2 via a second switch SW2.
- The other end of each of the multiple bit lines BL2 is electrically connected to a read circuit RC. The read circuit RC includes, for example, a read current circuit, a sense amplifier, etc. The read circuit RC may be electrically connected to each of the multiple bit lines BL1.
- For example, the first current source/sink circuit SSC1 supplies a write current Iw to the multiple bit lines BL1. Or, for example, the first current source/sink circuit SSC1 receives the write current Iw from the multiple bit lines BL1. For example, the second current source/sink circuit SSC2 supplies the write current Iw to the multiple bit lines BL2. Or, for example, the second current source/sink circuit SSC2 receives the write current Iw from the multiple bit lines BL2.
- The multiple word lines WL are electrically connected to a row decoder RD.
- For example, at least a portion of the first switch SW1, the second switch SW2, the first current source/sink circuit SSC1, the second current source/sink circuit SSC2, the read circuit RC, and the row decoder RD is included in the
controller 70. Thecontroller 70 may include thecontrol element 75. - For example, in the write operation, the first switch SW1, the second switch SW2, and the control element 75 (the
transistor 70T) that correspond to the selected cell (one of the multiple memory cells MC) are set to the on-state. For example, one of the first current source/sink circuit SSC1 or the second current source/sink circuit SSC2 functions as a current source. For example, the other of the first current source/sink circuit SSC1 or the second current source/sink circuit SSC2 functions as a current sink. The write current Iw flows in the selected cell in a direction corresponding to the information to be written. - For example, the write current Iw includes a current pulse. The pulse width of the current pulse is, for example, not less than several nanoseconds and not more than several microseconds. The write current Iw flows through the
magnetoresistive element 110 of the selected cell. For example, spin injection writing is performed by the write current Iw. - In the read operation, a read current is caused to flow in the
magnetoresistive element 110. The magnitude of the read current is smaller than the magnitude of the write current Iw. The sense amplifier of the read circuit RC senses a value (at least one of a current or a voltage) corresponding to the electrical resistance of themagnetoresistive element 110. - The
magnetic memory device 230 is, for example, spin injection-writing magnetic memory. -
FIG. 21 is a schematic view illustrating another magnetic memory device according to the second embodiment. - As shown in
FIG. 21 , themagnetic memory device 240 according to the embodiment includes thecontroller 70 and a magnetoresistive element or a modification of a magnetoresistive element according to the first embodiment. Themagnetoresistive element 110 is provided in the example. Themagnetoresistive element 110 includes the firstmagnetic layer 11, the secondmagnetic layer 12, and the firstnonmagnetic layer 11N. - The first
magnetic layer 11 is provided between the secondconductive layer 12E and a portion (a third portion 11Ec described below) of the firstconductive layer 11E. The secondmagnetic layer 12 is provided between the firstmagnetic layer 11 and the secondconductive layer 12E. The firstnonmagnetic layer 11N is provided between the firstmagnetic layer 11 and the secondmagnetic layer 12. The firstconductive layer 11E is electrically connected to the firstmagnetic layer 11. The secondconductive layer 12E is electrically connected to the secondmagnetic layer 12. - The
controller 70 is electrically connected to a first portion 11Ea of the firstconductive layer 11E. For example, the connection is performed by thefirst interconnect 70 a. Thecontroller 70 is electrically connected to a second portion 11Eb of the firstconductive layer 11E. For example, the connection is performed by athird interconnect 70 c. The third portion 11Ec recited above is provided between the first portion 11Ea and the second portion 11Eb. Thecontroller 70 is electrically connected to the secondconductive layer 12E (the second magnetic layer 12). - The
controller 70 implements a first operation and a second operation. In the first operation, thecontroller 70 supplies a first current Ic1 to the firstconductive layer 11E. The first current Ic1 flows from the first portion 11Ea toward the second portion 11Eb. In the second operation, thecontroller 70 supplies a second current Ic2 to the firstconductive layer 11E. The second current Ic2 flows from the second portion 11Eb toward the first portion 11Ea. - The electrical resistance between the first
magnetic layer 11 and the secondmagnetic layer 12 after the first operation recited above is different from the electrical resistance between the firstmagnetic layer 11 and the secondmagnetic layer 12 after the second operation recited above. - For example, the magnetization of the first
magnetic layer 11 after the first operation recited above is in a state corresponding to the orientation of the first current Ic1 recited above. The magnetization of the firstmagnetic layer 11 after the second operation recited above is in a state corresponding to the orientation of the second current Ic2 recited above. For example, this is based on spin-orbit coupling. For example, this is based on spin-Hall effect. - For example, the angle between the magnetization of the first
magnetic layer 11 and the magnetization of the secondmagnetic layer 12 after the first operation recited above is different from the angle between the magnetization of the firstmagnetic layer 11 and the magnetization of the secondmagnetic layer 12 after the second operation recited above. - For example, the
magnetoresistive element 110 is selected by a voltage applied between the firstconductive layer 11E and the secondconductive layer 12E. The magnetization of the firstmagnetic layer 11 is controlled by the voltage and the orientation of the current recited above. - According to the embodiments, a magnetoresistive element and a magnetic memory device can be provided in which the magnetoresistance ratio can be improved.
- In the specification of the application, “perpendicular” and “parallel” refer to not only strictly perpendicular and strictly parallel but also include, for example, the fluctuation due to manufacturing processes, etc. It is sufficient to be substantially perpendicular and substantially parallel.
- Hereinabove, exemplary embodiments of the invention are described with reference to specific examples. However, the embodiments of the invention are not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriately selecting specific configurations of components included in magnetoresistive elements or magnetic memory devices such as magnetic layers, intermediate layers, conductive layers, control elements, interconnects, controllers, etc., from known art. Such practice is included in the scope of the invention to the extent that similar effects thereto are obtained.
- Further, any two or more components of the specific examples may be combined within the extent of technical feasibility and are included in the scope of the invention to the extent that the purport of the invention is included.
- Moreover, all magnetoresistive elements and magnetic memory devices practicable by an appropriate design modification by one skilled in the art based on the magnetoresistive elements and the magnetic memory devices described above as embodiments of the invention also are within the scope of the invention to the extent that the spirit of the invention is included.
- Various other variations and modifications can be conceived by those skilled in the art within the spirit of the invention, and it is understood that such variations and modifications are also encompassed within the scope of the invention.
- While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.
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